### Install ORCA on Linux/MacOS/Windows via Command Line

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/faq

This snippet provides commands for installing ORCA using the command-line installer on Linux and MacOS. It covers making the installer executable, running it, and using advanced options for specifying installation paths or extracting files. The installer sets the path automatically.

```Shell
chmod a+x orca_6_0_0_linux_x86-64_shared_openmpi416.run
```

```Shell
./orca_6_0_0_linux_x86-64_shared_openmpi416.run
```

```Shell
  -i        : Set a different install path interactively
  -p <path> : Set a different install path
  -x        : Just extract
```

```Shell
./orca_6_0_0_linux_x86-64_shared_openmpi416.run -- -p /my/home/orca/dir
```

--------------------------------

### Run ORCA Calculation from Command Line

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/faq

This snippet shows how to start an ORCA calculation from the command line on all platforms (Linux, MacOS, Windows). It requires navigating to the directory containing the input file and executing the ORCA binary with the input and output file redirection.

```Shell
<full orca binary folder path>/orca example.inp > example.out
```

--------------------------------

### ORCA Installer Command-Line Options

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/faq.md

These options provide advanced control over the ORCA installer's behavior. Users can specify a custom installation path interactively or directly, or choose to only extract the installation files without performing a full setup.

```Bash
  -i        : Set a different install path interactively
  -p <path> : Set a different install path
  -x        : Just extract
```

--------------------------------

### Example Pre-filled ORCA LFT Input for Ni(II) 2p3d

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/utilities.md

This snippet provides an example of an ORCA LFT input file for Ni(II) 2p3d, where LFT parameters are automatically filled from an internal NEVPT2 database. This input is essentially ready to run, simplifying the setup process.

```orca
%lft

#-----Parameters------
NEl= 14
LFTCase 2p3d
Mult= 3, 1
NRoots= 25, 30
#--------------------

#---Slater-Condon Parameters---
#---All Values in eV---
PARAMETERS
F0pp =  85.88
F2pp =  54.77
F0dd =  23.31
F2dd =  13.89
F4dd =  9.14
F0pd =  33.03
F2pd =  7.76
G1pd =  6.42
G3pd =  2.11
end
#--------------------

#---Diagonal LFT-Matrix Elelemnts---
#---All Values in eV---
FUNCTIONS
0   0 " 0.00"
1   1 " 0.00"
2   2 " 0.00"
3   3 "1138.35"
4   4 "1138.35"
5   5 "1138.35"
6   6 "1138.35"
7   7 "1138.35"
end
#--------------------

#---SPECTRA/PROPERTIES---
DoABS true
#---------
end

*xyz 2 3
Ni 0.00 0.00 0.00
*
```

--------------------------------

### Execute ORCA Installer with Custom Installation Path

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/faq.md

This command demonstrates how to run the ORCA installer while specifying a non-default installation directory. The `--` separator is crucial to pass installer-specific options.

```Bash
./orca_6_0_0_linux_x86-64_shared_openmpi416.run -- -p /my/home/orca/dir
```

--------------------------------

### Execute ORCA Installer on Linux/MacOS

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/faq.md

This command initiates the ORCA installation process on Linux and MacOS. The installer will install ORCA in a user directory and set the path.

```Bash
./orca_6_0_0_linux_x86-64_shared_openmpi416.run
```

--------------------------------

### ORCA MD Input Example with Initial Setup

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/moldyn

This snippet demonstrates a complete ORCA input file activating the molecular dynamics module and defining an MD simulation block. It includes settings for timestep, initial velocities, thermostat, trajectory dumping, and the number of simulation steps, followed by molecular coordinates.

```SANscript
! MD BLYP D3 def2-SVP
%md
  Timestep 0.5_fs # This is a comment
  Initvel 350_K
  Thermostat NHC 350_K Timecon 10.0_fs
  Dump Position Stride 1 Filename "trajectory.xyz"
  Run 200
end
* xyz 0 1
O         -4.54021        0.78439        0.09307
H         -3.64059        0.38224       -0.01432
H         -4.63463        1.39665       -0.67880
*
```

--------------------------------

### Example ORCA Property Component

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/property_file

Shows the syntax of a single component within an ORCA property block, starting with '&' and including type information and its value.

```ORCA Property File Format
   &SCF_ENERGY [&Type "Double"]      -1.1271129230772137e+00
```

--------------------------------

### ORCA: Simple Input File Structure Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/structure.md

Illustrates the fundamental structure of an ORCA input file, combining keyword lines (starting with '!'), input blocks (enclosed by '%' and 'end'), and coordinate specifications (between '*' symbols). This example defines a Hartree-Fock calculation with a def2-TZVP basis set, tight SCF convergence, and coordinates for a CO molecule.

```orca
! HF def2-TZVP

%scf
   convergence tight
end

* xyz 0 1
C  0.0  0.0  0.0
O  0.0  0.0  1.13
*
```

--------------------------------

### Example ORCA_LFT Input with NEVPT2 Parameters for Ni(II)

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/utilities

This snippet provides a ready-to-run `orca_lft` input file for the Ni(II) 2p3d LFT case. The LFT parameters are automatically filled in from an internal NEVPT2 database, demonstrating a pre-configured setup for simulations.

```ORCA input
%lft

#-----Parameters------
NEl= 14
LFTCase 2p3d
Mult= 3, 1
NRoots= 25, 30
#--------------------

#---Slater-Condon Parameters---
#---All Values in eV---
PARAMETERS
F0pp =  85.88
F2pp =  54.77
F0dd =  23.31
F2dd =  13.89
F4dd =  9.14
F0pd =  33.03
F2pd =  7.76
G1pd =  6.42
G3pd =  2.11
end
#--------------------

#---Diagonal LFT-Matrix Elelemnts---
#---All Values in eV---
FUNCTIONS
0   0 " 0.00"
1   1 " 0.00"
2   2 " 0.00"
3   3 "1138.35"
4   4 "1138.35"
5   5 "1138.35"
6   6 "1138.35"
7   7 "1138.35"
end
#--------------------

#---SPECTRA/PROPERTIES---
DoABS true
#---------
end

*xyz 2 3
Ni 0.00 0.00 0.00
*
```

--------------------------------

### ORCA Utility: orca_loc Program Documentation

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/casscf

This section describes the `orca_loc` utility program, which is used for localizing orbitals from a gbw file. It notes that running `orca_loc` from the shell provides a help-file with details on input setup and refers to the ORCA manual for comprehensive documentation.

```APIDOC
Program: orca_loc
  Purpose: Localize orbitals from a gbw file.
  Usage: Run 'orca_loc' in shell for help on input setup.
  Documentation: Refer to 'orca_loc' section in ORCA manual (utilities.html#sec-utilities-loc-detailed).
```

--------------------------------

### Initial ORCA DOCKER Output: Setup and Host/Guest Optimization

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/typical/docker.md

This ORCA output segment displays the initial information from a DOCKER run, confirming the guest file, number of structures, and charge/multiplicity. It also indicates the start of host and guest geometry optimizations, which by default use the GFN2-XTB method.

```orca
                               ***************
                               * ORCA Docker *
                               ***************

Reading guests from file             water.xyz
Number of structures read from file  1
Charge and multiplicity of guest     from file
Docking approach                     independent
Docking level                        normal
Optimizing host                      .... -5.070544 Eh
Optimizing guest                     .... -5.070544 Eh
```

--------------------------------

### ORCA Output: Average Natural Orbital Occupation Numbers (AANOs)

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/typical/mrci

Displays the occupation numbers for the average natural orbitals. This analysis is crucial for identifying orbitals that are significantly occupied but might have been excluded from the active space, guiding improvements to the calculation setup.

```ORCA Output
------------------------
AVERAGE NATURAL ORBITALS
------------------------

Trace of the density to be diagonalized = 12.000000
Sum of eigenvalues = 12.000000
Natural Orbital Occupation Numbers:
N[  2] ( A1)=   1.99831062
N[  3] ( A1)=   1.99761604
N[  4] ( A1)=   1.99479313
N[  5] ( B1)=   1.99016881
N[  6] ( B2)=   1.95818285
N[  7] ( B1)=   1.33014178
N[  8] ( B2)=   0.70688423
N[  9] ( B1)=   0.00988561
N[ 10] ( A1)=   0.00436843
```

--------------------------------

### Exploring Alternative Initial Guess Methods

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/tipps.md

Experiment with different initial guess methods like Hueckel, PAtom, or HCore to find a better starting point for SCF convergence.

```ORCA Configuration
Guess=Hueckel
Guess=PAtom
Guess=HCore
```

--------------------------------

### ORCA Output: Initial Guess Calculation Steps

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/tutorials/first_steps/input_output

This snippet illustrates the steps involved in building the initial guess for the calculation, showing the progression of various initialization and setup tasks such as loading densities, setting up the integral package, and diagonalizing the Hamiltonian.

```ORCA Output
------------------------------
INITIAL GUESS: MODEL POTENTIAL
------------------------------
Loading Hartree-Fock densities                     ... done
Calculating cut-offs                               ... done
Initializing the effective Hamiltonian             ... done
Setting up the integral package (SHARK)            ... done
Starting the Coulomb interaction                   ... done (   0.0 sec)
Making the grid                                    ... done (   0.0 sec)
Mapping shells                                     ... done
Starting the XC term evaluation                    ... done (   0.0 sec)
Transforming the Hamiltonian                       ... done (   0.0 sec)
Diagonalizing the Hamiltonian                      ... done (   0.0 sec)
Back transforming the eigenvectors                 ... done (   0.0 sec)
Now organizing SCF variables                       ... done
```

--------------------------------

### Demonstrate GoTo Command Usage in ORCA Compound Script

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/compound_examples

This brief ORCA compound script serves as a minimal example to illustrate the functionality and syntax of the `GoTo` command within ORCA's scripting environment. It highlights how control flow can be managed using this command.

```ORCA Script
# Compound Example on GoTo usage
```

--------------------------------

### Get Second Dimension Size of Variable Array (V.GetDim2) Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/compound

Example script demonstrating the V.GetDim2() function, showing its behavior for scalar, 1D, and 2D array variables. Also includes GetDim1 and GetSize.

```ORCA Script
# ----------------------------------------------------
# This is an example script for
#  Variable functions
# -----------------------------------------------------
%Compound
  Variable dim1, dim2, size;
  Variable A;
  Variable B[3];
  Variable C[3][2];

  print("----------------------------------------\n");
  print("          Results for scalar  \n");
  print("Dim1 : %d (it should print 1)\n", A.GetDim1());
  print("Dim2 : %d (it should print 1)\n", A.GetDim2());
  print("Size : %d (it should print 1)\n", A.GetSize());
  print("----------------------------------------\n");
  print("          Results for 1D-Array  \n");
  print("Dim1 : %d (it should print 3)\n", B.GetDim1());
  print("Dim2 : %d (it should print 1)\n", B.GetDim2());
  print("Size : %d (it should print 3)\n", B.GetSize());
  print("----------------------------------------\n");
  print("          Results for 2D-Array  \n");
  print("Dim1 : %d (it should print 3)\n", C.GetDim1());
  print("Dim2 : %d (it should print 2)\n", C.GetDim2());
  print("Size : %d (it should print 6)\n", C.GetSize());
End
```

--------------------------------

### Get First Dimension Size of Variable Array (V.GetDim1) Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/compound

Example script demonstrating the V.GetDim1() function, showing its behavior for scalar, 1D, and 2D array variables. Also includes GetDim2 and GetSize.

```ORCA Script
# ----------------------------------------------------
# This is an example script for
#  Variable functions
# -----------------------------------------------------
%Compound
  Variable dim1, dim2, size;
  Variable A;
  Variable B[3];
  Variable C[3][2];

  print("----------------------------------------\n");
  print("          Results for scalar  \n");
  print("Dim1 : %d (it should print 1)\n", A.GetDim1());
  print("Dim2 : %d (it should print 1)\n", A.GetDim2());
  print("Size : %d (it should print 1)\n", A.GetSize());
  print("----------------------------------------\n");
  print("          Results for 1D-Array  \n");
  print("Dim1 : %d (it should print 3)\n", B.GetDim1());
  print("Dim2 : %d (it should print 1)\n", B.GetDim2());
  print("Size : %d (it should print 3)\n", B.GetSize());
  print("----------------------------------------\n");
  print("          Results for 2D-Array  \n");
  print("Dim1 : %d (it should print 3)\n", C.GetDim1());
  print("Dim2 : %d (it should print 2)\n", C.GetDim2());
  print("Size : %d (it should print 6)\n", C.GetSize());
End
```

--------------------------------

### Divide ORCA Forcefield File Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/typical/qmmm

Example command demonstrating how to split an ORCAFF.prms file into a new file starting from a specific atom number (e.g., for a ligand) using the `orca_mm -splitff` option.

```Shell
orca_mm -splitff 1C1E_substrate_noH.ORCAFF.prms 7208
```

--------------------------------

### orca_2json Comprehensive Configuration File Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/orca_2json.md

A detailed example of an `orca_2json` configuration file, demonstrating how to selectively enable/disable various data types, request specific 1-electron and 2-electron integrals, specify density types, and define output JSON formats.

```orca
{
	"MOCoefficients": false,
	"Basisset": true,
	"1elPropertyIntegrals": ["dipole", "quadrupole", "velocity", "printLinMom", "angular_momentum", "higherMoment"],
	"1elPropertyRelIntegrals": ["dipole", "quadrupole", "angular_momentum"],
	"1elIntegrals": ["H", "S", "T", "V", "HMO"],
	"1elIntegralsRel": ["H", "S", "T", "V", "HMO"],
	"Vaux": false,
	"AuxBasisType": "AuxC",
	"FullTrafo": false,
	"OrbWin": [0,0,0,0,0,0,0,0],
	"2elIntegrals": [ "MO_IJKL", "RI_IAV", "RI_IJKL"],
	"2elNonRedIntegrals": false,
	"2elNonRedRIIntegrals": false,
	"MullikenCharge": false,
	"LoewdinCharge": false,
	"Densities": ["all"],
	"JSONFormats": ["json", "bson"]
}
```

--------------------------------

### Get Total Timer Value (ORCA Script)

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/compound

The Total() function returns the cumulative time recorded by a timer object since its last Start() or Reset() call. The value is returned as a real number. This function is used to get the overall duration of a timed operation.

```Custom Script
# -----------------------------------------------
# This is to test timer functions.
# --------------------------------
timer tm;
Variable x = 0.0;
tm.start();
for index from 0 to 100000 Do
  x = x + 0.1;
EndFor
tm.stop();
x = tm.Total();
print( "------------------------------\n");
print( "   Compound - Timer Results   \n");
print( "------------------------------\n");
print( " First total time:   %.2lf\n", x);

x = tm.total();
tm.Reset();
tm.Start();
for index from 0 to 200000 Do
  x = x + 0.1;
EndFor
tm.Stop();
x = tm.total();

print( " Second total time:   %.2lf\n", x);
End
```

--------------------------------

### Example ORCA Input for QM/QM2/MM Calculation

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/typical/qmmm.md

Provides a comprehensive example ORCA input file for a QM/QM2/MM calculation, demonstrating the setup of force field, QM atoms, QM2 atoms, active atoms, and medium system charge, along with common calculation keywords.

```orca
!QM/HF-3c/MM Opt B3LYP def2-TZVP def2/J NumFreq
%qmmm
 ORCAFFFilename "peptideChain.ORCAFF.prms"
 QMAtoms {16:33 68:82} end
 QM2Atoms {0:12 83:104} end
 ActiveAtoms { 0:38 65:120} end
 Charge_Medium 0
end
*pdbfile -1 1 peptideChain.pdb
```

--------------------------------

### Get Last Timer Value (T.Last) in Compound Language

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/compound.md

The Last function, applied to a timer object, returns the real number value of the timer's last recorded duration. It is crucial that the timer object has been initialized and started using the 'Start' function before calling 'Last'.

```orca
myTimer.Last();
```

--------------------------------

### Console Output for Initial orca_crystalprep Input Generation

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/utilities

This snippet shows the standard console output confirming that the `crystalprep.inp` file has been successfully generated by the `orca_crystalprep` tool. It indicates that the initial setup process is complete.

```text
---------------------------------------------------------------------------------
Initial Input: crystalprep.inp for Orca_CrystalPrep has been generated. All Done!
---------------------------------------------------------------------------------
```

--------------------------------

### Running `orcacclib` for Sequential Coupling Coefficient Generation

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/iceci.md

Illustrates the basic command-line usage of the `orcacclib` utility to pre-tabulate one-particle coupling coefficients. This program takes the desired multiplicity and maximum number of open shells as arguments, producing binary files (`orcacc.el.mult.nopen` and `orcacc.sp.mult.nopen`) that can be reused in subsequent ORCA calculations to save time.

```orca
orca_cclib Mult MaxNOpen
```

--------------------------------

### MCD Calculation in ROCIS Module Input Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/mcd.md

Example ORCA input file demonstrating the setup for MCD calculations within the ROCIS module. It is essential to include the `NewMCD True` keyword in the `%selected module` block to invoke the updated MCD implementation.

```orca
! ROCIS calculation with MCD
! This is a placeholder for ../../orca_working_input/MCDROCIS.inp

%selected module
  NewMCD True
  DoMCD True
  MCDGridtype 1
  MCDLebedev 14
  B 3000.0
  Temperature 300.0
end

! Other ORCA input sections (e.g., basis, method, coordinates)
*xyz 0 1
  O 0.0 0.0 0.0
  H 0.96 0.0 0.0
  H -0.24 0.93 0.0
* 
```

--------------------------------

### ORCA Docking Configuration Tips

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/docker

A collection of general tips and commands for configuring and optimizing the docking process in ORCA, covering PES selection, docking speed, procedure levels, structure optimization, and topology checks.

```ORCA Configuration
!DOCK(GFN2-XTB)
!DOCK(GFN1-XTB)
!DOCK(GFN0-XTB)
!DOCK(GFN-FF)
```

```ORCA Configuration
!QUICKDOCK
```

```ORCA Configuration
%DOCK DOCKLEVEL COMPLETE END
# Other levels: SCREENING, QUICK, NORMAL (default), COMPLETE
```

```ORCA Configuration
%DOCKER
  NOPT <value>
END
```

```ORCA Configuration
%DOCK CHECKGUESTTOPO FALSE END
```

--------------------------------

### Assign Array Variables in ORCA Input

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/structure

Shows different ways to assign values to array variables in ORCA. Arrays are 0-indexed. Examples include assigning to a specific index, assigning multiple values starting from an index, and assigning multiple values starting from index 0.

```ORCA Input
Array[1]  Value1
Array[1]  Value1,Value2,Value3
Array  Value1,Value2

```

--------------------------------

### Control Flow: For Loop Syntax and Example in ORCA

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/compound.md

The For loop in ORCA is used for repetitive tasks, iterating a variable from a start to an end integer value, inclusive. It supports using numbers, predefined variables, or functions for start and end values. The loop body executes commands between 'Do' and 'EndFor'.

```orca
For variable From Start value To End value Do
  commands
EndFor or EndFor;
```

```orca
For i From 1 To 10 Do
  Print "Iteration: ", i;
EndFor;
```

--------------------------------

### Start ORCA Calculation from Command Line

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/faq.md

This command initiates an ORCA quantum chemistry calculation using a specified input file and redirects the output to an output file. It's applicable for both Linux/MacOS and Windows command-line environments.

```Bash
<full orca binary folder path>/orca example.inp > example.out
```

```CMD
<full orca binary folder path>/orca example.inp > example.out
```

--------------------------------

### ORCA DOCKER Output: Detailed Process Initialization

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/typical/docker.md

This ORCA output section provides a detailed breakdown of the DOCKER calculation's initialization. It includes guest properties, the chosen PES (GFN2-XTB), spatial grid parameters like dimensions and step sizes, and the setup of workers for the evolutionary algorithm, including population density and size.

```orca
Starting Docker
---------------
Guest structure                      .... structure number 1
Guest charge and multiplicity        .... (0 , 1)
Final charge and multiplicity        .... (0 , 1)
PES used during evolution            .... GFN2-XTB
Setting random seed                  .... done
Creating spatial grid
   Grid Max Dimension                5.50 Angs
   Angular Grid Step                 32.73 degrees
   Cartesian Grid Step               0.50 Angs
   Points per Dimension              11 points
Initializing workers
   Population Density                0.50 worker/Ang^2
   Population Size                   57
Evolving structures
   Minimization Algorithm            mutant particle swarm
   Min, Max Iterations               (3 , 10)
```

--------------------------------

### ORCA SOLVATOR Stochastic Mode Output Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/solvator.md

Example output showing the iteration, target function value, and time for solvent placement in ORCA's 'STOCHASTIC' mode. The 'Target function' represents the minimized value V, which guides solvent positioning to maximize electrostatic interactions and minimize distance.

```orca
      Iter     Target function   Time
                                (min)
      -------------------------------
         1     -4.342597e-07     0.00
         2     -3.166857e-07     0.00
         3     -4.814590e-08     0.00
```

--------------------------------

### Example Metainfo File Content

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/utilities

A simple example of content found in a `*.metainfo` file, which receives information like atom type assignments, charges, and spins for use in subsequent calculations.

```Configuration
18522
```

--------------------------------

### ORCA Input Example: ROHF Reference with AUTOCI UHF

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/autoci

Illustrates an ORCA input file setup for performing UHF calculations with an ROHF reference using the AUTOCI module. This example includes the `RunROHFasUHF` flag and a basic molecular geometry, along with an EPRNMR property calculation.

```ORCA Input
! ROHF def2-svp tightscf pmodel AUTOCI-CCSD

%autoci
    RunROHFasUHF true
end

* xyz 0 2
Cu  0.0  0.0  0.0
*

%eprnmr nuclei = all Cu {aiso} end
```

--------------------------------

### Run ORCA LFT Standalone with Input File

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/utilities.md

Demonstrates how to execute the `orca_lft` program directly by providing an input file (Basename.lft.inp) and the `-sim` flag for simulation.

```orca
orca_lft BaseName.lft.inp -sim
```

--------------------------------

### Example: Generate NaCl Embedding Cluster Input for IC-QM/MM

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/utilities

This `crystalprep.inp` example demonstrates a complete setup for generating an embedding cluster input for NaCl. It includes reading the `nacl.cif` file, creating a 20x20x20 supercell, defining atom types for Na and Cl with their respective charges and spins, and configuring for IC-QM/MM input generation.

```text
%crystalprep

#************************
#Read CIF/XYZ
#************************
DoCIF true

#------------------------
#INPUT CIF/XYZ
#------------------------
InputCIF "nacl.cif"

#************************
#Generate SuperCell
#************************
DoSuperCell true
SCDimension "20x20x20"

#************************
#Setup Embedding Approach
#************************
DoEmbedding true
DoLayers true

#------------------------
#Atom Type Charge Spin
#------------------------
NAtomTypes 2
Na 0  1.0  0.0
Cl 1 -1.0  0.0

#************************
#Generate Inputs
#************************
DoICQMMMInput true
QCCharge 0
QCMult 1
#------------------------
end
```

--------------------------------

### Example Content for Custom QM2 Method File

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/typical/qmmm

Provides an example of the content that can be included in a custom QM2 method file (e.g., myQM2Method.txt), demonstrating how to specify methods, convergence settings, and basis sets.

```ORCA Input
!cc-pVDZ HF TightSCF NOSOSCF KDIIS
%basis
  NewAuxJKGTO Mg "AutoAux" end
end
```

--------------------------------

### orca_crystalprep Command Line Usage and Options

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/utilities.md

This section outlines the command-line usage patterns for `orca_crystalprep`, detailing how to generate an initial input file or process an existing CrystalPrep input. It also lists the primary command-line options available.

```APIDOC
************************************************************************************************************
Generate initial ORCA CrystalPrep Input
************************************************************************************************************

============================================================================================================
Usage: orca_crystalprep [Basename Input] [options]
============================================================================================================

------------------------------------------------------------------------------------------------------------
[Options]:
------------------------------------------------------------------------------------------------------------
-geninput                     Generate Initial Input
------------------------------------------------------------------------------------------------------------

************************************************************************************************************
Generate ORCA Embedding Cluster Inputs using the CrystalPrep Utility
************************************************************************************************************

============================================================================================================
Usage: orca_crystalprep [CrystalPrep Input]
============================================================================================================
```

--------------------------------

### Define a Method Block in ORCA Input

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/structure

Demonstrates the basic syntax for defining an input block in ORCA, starting with '%' and ending with 'end'. This example sets the computation method to Hartree-Fock (HF).

```ORCA Input
%method  method HF
         end

```

--------------------------------

### Pople-style Basis Sets Reference

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/structure.md

Lists common Pople-style basis sets and their elemental coverage for use in quantum chemistry calculations.

```APIDOC
STO-3G: Minimal basis set(H--I)
3-21G: Pople 3-21G (H--Cs)
3-21GSP: Buenker 3-21GSP (H--Ar)
4-22GSP: Buenker 4-22GSP (H--Ar)
6-31G: Pople 6-31G and its modifications (H--Zn)
m6-31G: Modified 6-31G for 3d transition metals (Sc--Cu)
6-311G: Pople 6-311G and its modifications (H--Br)
```

--------------------------------

### Running `orcacclib` with MPI for Parallel Coupling Coefficient Generation

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/iceci.md

Demonstrates how to execute the `orcacclib` utility in parallel using `mpirun` to accelerate the generation of coupling coefficient libraries. This command specifies the number of processes and the full path to the MPI-enabled `orca_cclib_mpi` executable, along with the required multiplicity, maximum number of open shells, and a `cclib` flag.

```orca
mpirun -np 4 /full_path/orca_cclib_mpi Mult MaxNOpen cclib  # using 4 processes
```

--------------------------------

### Compound Timer Object Usage Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/compound

This script demonstrates the declaration and usage of a Timer object in Compound. It measures the execution time of two loops using start(), stop(), and total() functions, and shows how to reset the timer.

```Compound
# -----------------------------------------------
# This is to test timer functions.
# --------------------------------
timer tm;
Variable x = 0.0;
tm.start();
for index from 0 to 100000 Do
  x = x + 0.1;
EndFor
tm.stop();
x = tm.Total();
print( "------------------------------\n");
print( "   Compound - Timer Results   \n");
print( "------------------------------\n");
print( " First total time:   %.2lf\n", x);

x = tm.total();
tm.Reset();
tm.Start();
for index from 0 to 200000 Do
  x = x + 0.1;
EndFor
tm.Stop();
x = tm.total();

print( " Second total time:   %.2lf\n", x);
End
```

--------------------------------

### ORCA_LFT Input File Example for NEVPT2

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/casscf.md

Provides a detailed example of an `orca_lft` input file (`fe.2p3d.nevpt2.lft.inp`) for a NEVPT2 calculation. It specifies parameters like the number of electrons, shell quantum numbers, multiplicity, number of roots, Slater-Condon parameters, LFT matrix elements, SOC constants, and spectral properties such as absorption (DoABS).

```ORCA Input
%lft

#-----Parameters------
NEl= 12
Shell_PQN= 0, 2, 3, 0
Mult= 5, 3
NRoots= 65, 330
#--------------------

#---Slater-Condon Parameters---
#---All Values in eV---
PARAMETERS
F0pp =  95.9866
F2pp =  51.8683
F0dd =  21.9936
F2dd =  11.6097
F4dd =  7.5716
F0pd =  45.1006
F2pd =  5.4055
G1pd =  5.6086
G3pd =  3.4878
end
#--------------------

#---LFT-Matrix Elelemnts---
#---All Values in eV---
FUNCTIONS
0   0   "  0.0000"
1   0   " -0.0146"
1   1   "  0.0947"
2   0   "  0.0210"
2   1   "  0.0061"
2   2   "  0.1155"
3   0   "  0.0000"
3   1   " -0.0000"
3   2   " -0.0000"
3   3   "1086.2398"
4   0   "  0.0000"
4   1   " -0.0000"
4   2   " -0.0000"
4   3   "  0.0323"
4   4   "1086.2181"
5   0   " -0.0000"
5   1   "  0.0000"
5   2   "  0.0000"
5   3   " -0.0356"
5   4   " -0.0154"
5   5   "1086.1183"
6   0   "  0.0000"
6   1   " -0.0000"
6   2   " -0.0000"
6   3   " -0.0767"
6   4   " -0.0080"
6   5   "  0.0341"
6   6   "1086.1219"
7   0   " -0.0000"
7   1   "  0.0000"
7   2   "  0.0000"
7   3   "  0.0050"
7   4   " -0.0023"
7   5   "  0.0026"
7   6   " -0.0038"
7   7   "1086.0688"
end
#--------------------

#---SOC-CONSTANTS---
#---All Values in eV---
PARAMETERS
ZETA_P = 8.06
ZETA_D = 0.06
end
#--------------------

#---SPECTRA/PROPERTIES---
DoABS true
#------------------------
end

*xyz Charge Multiplicity
Atom 0.00 0.00 0.00
*
```

--------------------------------

### Executing POLY_ANISO Program via Bash

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/poly_aniso.md

This snippet demonstrates the command-line execution of the `POLY_ANISO` program. It shows how to run the `otool_poly_aniso` executable, redirecting `poly_aniso.input` as standard input and `poly_aniso.output` as standard output. The input and output file names are not hardcoded and can be customized.

```sh
bash:$
bash:$  $ORCA/x86_64/otool_poly_aniso  <  poly_aniso.input   >  poly_aniso.output
bash:$
```

--------------------------------

### ORCA Compound Script: Hello World Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/compound_examples

This is the simplest ORCA Compound script, demonstrating its ability to act as a driver for various tasks beyond standard ORCA calculations, such as printing a message. The script is typically saved as 'helloWorld.inp'.

```ORCA Compound Script
%Compound
  print("Hellow World!\n");
EndRun

```

--------------------------------

### Array Type Component Example

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/property_file

Shows a component with an 'ArrayOfDoubles' type, including dimension information and an array of double values, typically starting from the next line with a row index.

```ORCA Property File Format
   &DIPOLETOTAL [&Type "ArrayOfDoubles", &Dim (3,1)] "Total"
                                                         0

0                                      0.0000000000000000e+00
1                                      0.0000000000000000e+00
2                                     -5.1833121128553384e-12
```

--------------------------------

### Execute ORCA Calculation

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/tutorials/first_steps/first_calc

Command to run the ORCA program with the specified input file 'water.inp'. This initiates the quantum chemistry calculation defined in the input file, printing the output to the screen.

```Bash
orca water.inp
```

--------------------------------

### Example ORCA Property Block

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/property_file

Demonstrates the general structure of a property block, starting with '$' and ending with '$End', containing components like 'GeometryIndex', 'ListStatus', and a specific property value.

```ORCA Property File Format
$SCF_Energy
   &GeometryIndex 1
   &ListStatus       OUT
   &SCF_ENERGY [&Type "Double"]      -1.1271129230772137e+00
$End
```

--------------------------------

### ORCA Input: IMDHO Model Example File (`example002.inp`)

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/asa.general.md

An example ORCA input file (`example002.inp`) demonstrating the configuration for simulating vibrational structure in absorption and fluorescence spectra using the IMDHO model. This setup assumes an origin shift of the excited potential energy surface along five normal coordinates.

```ORCA Input
# example002.inp
#
# Input file for simulation  of vibrational structure
# in absorption and fluorescence spectra assuming
# origin shift of excited PES along 5 normal coordinates.
```

--------------------------------

### ONIOM Configuration Summary Output

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/tutorials/multi/basics

This snippet shows the initial configuration summary for a 2-layered ONIOM calculation. It details the multiscale model (QM1/QM2), the QM2 method (XTB2), and the default coupling and embedding schemes (subtractive and electrostatic, respectively). It also provides the size of the full system and its QM1 and QM2 subsystems in atoms.

```Program Output
                     **************************
                     *    2-layered ONIOM     *
                     **************************
(...)
Multiscale model                       ... QM1/QM2
QM2 method                             ... XTB2
Coupling Scheme                        ... subtractive
Embedding Scheme                       ... electrostatic
(...)
Size of different subsystems (in atoms):
Size of QMMM System                    ... 24
Size of QM2 Subsystem                  ... 12
Size of QM1 Subsystem                  ... 12
(...)
```

--------------------------------

### Get Bond Distance Between Two Atoms (ORCA)

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/compound.md

Function GetBondDistance acts on geometry objects and returns the distance between two atoms in Bohrs. It requires a loaded geometry object and the indices of the two atoms. Indices start counting from 0.

```APIDOC
Function: G.GetBondDistance
Syntax: res = geom.GetBondDistance(atomA, atomB)
Parameters:
  geom: A geometry object previously loaded.
  atomA: The index of atomA in the geometry (0-indexed).
  atomB: The index of atomB in the geometry (0-indexed).
Returns:
  res: The distance between atoms atomA and atomB in Bohrs.
```

```orca
# Example ORCA input for G.GetBondDistance
# This file would contain ORCA commands to load a geometry
# and then call geom.GetBondDistance(atomA, atomB)
# For instance:
# %geometry
#   load "my_geometry.xyz"
# %end
# bond_distance = geom.GetBondDistance(0, 1)
```

--------------------------------

### Create and Navigate to Calculation Directory (Windows)

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/tutorials/first_steps/first_calc

Commands to create a new directory named 'firstcalc' in the C: drive and then navigate into it on Windows systems. This helps in organizing ORCA calculations.

```CMD
mkdir C:\firstcalc
cd C:\firstcalc
```

--------------------------------

### ORCA Metadynamics Setup for Two-Dimensional Simulation

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/moldyn.md

Example ORCA commands to set up a two-dimensional Metadynamics simulation. It defines two collective variables (distance and angle) using `Manage_Colvar` and then applies `Metadynamics` with `Colvar` and `Scale` modifiers to each.

```orca
Manage_Colvar Define 1 Distance Atom 0 Atom 1
Manage_Colvar Define 2 Angle Atom 0 Atom 1 Atom 2
Metadynamics Colvar 1 Scale 1.0_A Colvar 2 Scale 10.0_Deg
```

--------------------------------

### Create and Navigate to Calculation Directory (Linux/Mac)

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/tutorials/first_steps/first_calc

Commands to create a new directory named 'firstcalc' in the user's home directory and then navigate into it on Linux or macOS systems. This is recommended for organizing ORCA calculations.

```Bash
mkdir ~/firstcalc
cd ~/firstcalc
```

--------------------------------

### Output Log: Configuration Interaction (CI) Problem Setup

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/utilities

This log section describes the process of defining and setting up the Configuration Interaction (CI) spaces. It shows the number of configurations, CSFs (Configuration State Functions), and roots for different multiplicities, including adjustments made to match the number of roots to CSFs, concluding with the successful setup of the CI problem.

```Output Log
Defining the CI spaces and setting up the CI             ...
Making Checks...
Multiplicty =   3, #(configurations) =     28 #(CSF's) =     28 #(Roots) =     25
NRoots<NCSFs Adjussting  ==> (CSF's) =     25
Setting up CI...
Multiplicty =   3, #(configurations) =     28 #(CSF's) =     25 #(Roots) =     25
Making Checks...
Multiplicty =   1, #(configurations) =     36 #(CSF's) =     36 #(Roots) =     30
NRoots<NCSFs Adjussting  ==> (CSF's) =     30
Setting up CI...
Multiplicty =   1, #(configurations) =     36 #(CSF's) =     30 #(Roots) =     30
CI setup done
```

--------------------------------

### ORCA NBO Program Interface Test

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/nbo

A basic example demonstrating the start of an ORCA input file configured to test the interface with the NBO program. This snippet shows a comment line typically found at the beginning of such input files.

```ORCA Input
#
# Test the interface to the NBO program

```

--------------------------------

### Assigning Values to Array Variables in ORCA Input

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/structure.md

These examples demonstrate different ways to assign values to array variables in ORCA. Arrays can be indexed explicitly (starting from 0) or values can be assigned sequentially to multiple array members on a single line.

```orca
Array[1]  Value1
```

```orca
Array[1]  Value1,Value2,Value3
```

```orca
Array  Value1,Value2
```

--------------------------------

### ORCA DOCKER Module Configuration

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/typical/docker.md

This snippet illustrates the use of simple keywords to set general docking parameters and the detailed %DOCKER block for advanced configuration. It covers specifying guest molecules, defining docking strategies (SCREENING, NORMAL, COMPLETE), repeating guest content, fixing host coordinates, selecting potential energy surfaces for evolution, and setting final optimization parameters.

```orca
!QUICKDOCK       # simple keyord to set DOCKLEVEL QUICK
!NORMALDOCK      # simple keyord to set DOCKLEVEL NORMAL
!COMPLETEDOCK    # simple keyord to set DOCKLEVEL COMPLETE

!DOCK(GFN-FF)    # simple keyord to set EVPES GFNFF
!DOCK(GFN0-XTB)  # simple keyord to set EVPES GFN0XTB
!DOCK(GFN1-XTB)  # simple keyord to set EVPES GFN1XTB
!DOCK(GFN2-XTB)  # simple keyord to set EVPES GFN2XTB

%DOCKER

   #
   # general options
   #

   GUEST           "filename.xyz" # an .xyz file (can be multistructure), from where
                                  # the guest(s) will be read. can contain different
                                  # charges and multiplicities for each guests on the
                                  # comment line. will only be read if exactly two
                                  # integer numbers are given, otherwise ignored.

   DOCKLEVEL       SCREENING  # defines a general strategy for docking.
                          # will alter things like that population density
                   NORMAL     # and final number of optimized structrures.
                   COMPLETE   # default is NORMAL.

   NREPEATGUEST    1          # number of times to repeat the content of the "GUEST" file
   CUMULATIVE      TRUE       # add the contents of the "GUEST" file one on
                              # top of each other?
                              # default is FALSE, meaning each will be done independently.

   FIXHOST         TRUE       # freeze coordinatef for the HOST during all steps?
                              # (default FALSE)

   #
   # evolution step
   #

   EVPES           GFNFF      # which PES to use **only** during the evolution step.
                   GFN0XTB    # can be different from the final optimization.
                   GFN1XTB
                   GFN2XTB
   #
   # final optimization
   #

   NOPT            10         # a fixed number of structures to be optimized
   NOOPT           FALSE      # do not optimize any structure at all? (default FALSE)
```

--------------------------------

### ORCA Script Variable Assignment Initialization

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/contents/detailed/compound

This snippet provides an example of initial variable declarations in ORCA Script, setting up various scalar and array variables (1D and 2D) that are intended for subsequent assignment operations. It serves as a setup for demonstrating different assignment methods.

```ORCA Script
# -------------------------------------------------------------
# This is to check all available ways of variable assignement
#   (It does not take care of 'with' we will have a separate
#         file for this)
# -------------------------------------------------------------

# -----------------------------------
# Some necessary initial declarations
# -----------------------------------
Variable x1, x2, x3, x4;
Variable y1, y2, y3, y4;
Variable x5[4];
Variable y5[4];
Variable x6[3][3];
Variable y6[3][3];

# -----------------------------------
# Now the assignements
```

--------------------------------

### ICE-CI Implementation Check Placeholder

Source: https://www.faccts.de/docs/orca/6.0/tutorials/orca/6.0/manual/_sources/contents/detailed/iceci.md

This minimal snippet acts as a comment or header within a configuration file, indicating the start of a section dedicated to checking the ICE-CI implementation for a simple calculation, such as on a water molecule.

```Configuration
#
# Check the ICECI implementation
```