ORCA

https://www.faccts.de/docs/orca/6.1/
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ORCA is an ab initio, DFT, and semiempirical SCF-MO package that enables users to perform...
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### Automated QM/MM Setup with ORCAFF

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/multiscalesimulations/qmmm-general.html

Configure automated QM/MM setup using ORCAFF parameters, specifying core atoms and fragmentation procedures. This example uses a PDB file for atom definition and requires ORCAFF parameter files.

```input
! QMMMSetup # just do the preparation and stop
! QMMM
%qmmm
  ORCAFFFilename "reactant.ORCAFF.prms"
  QMCoreAtoms {183 2745} end
  ActiveCoreAtoms {183 2745} end
  frag
    FragProc SEQBACKBONE, AASCFINEGRAINED, FUNCTIONALGROUPS, EXTEND, Connectivity
    UseTopology true
    TopolFile "reactant.ORCAFF.prms"
  end
end
*pdbfile 0 1 reactant.pdb


```

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

### Basic QM/QM2/MM Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/multiscalesimulations/qmmm-molecules.html

An example configuration for a QM/QM2/MM calculation, specifying the ORCA force field file, atom selections for QM and QM2 regions, active atoms, and system charge.

```qmmm
!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

```

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

### CIM-RI-MP2 Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/modelchemistries/mdci.md.txt

Example configuration for performing a CIM-RI-MP2 calculation. Specifies the RI-MP2 method, basis sets, and custom CIM threshold.

```orcainput
#
# CIM-RI-MP2 calculation
#
! RI-MP2 cc-pVDZ cc-pVDZ/C CIM
%CIM
  CIMTHRESH 0.0005  # Default value is 0.001
end

* xyzfile 0 1 CIM.xyz

```

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

### NEVPT2 Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/modelchemistries/NEVPT2.html

Example of setting up a NEVPT2 calculation using simple input or the %casscf block. Note the spelling difference between simple input ('SC-NEVPT2') and block input ('SC_NEVPT2').

```input
!def2-svp nofrozencore PAtom
%casscf nel  6
        norb 6
        mult 1
        PTMethod SC_NEVPT2 # SC_NEVPT2 for strongly contracted NEVPT2
                           # FIC_NEVPT2 for the fully internally
			   # contracted NEVPT2
                           # DLPNO_NEVPT2 for the FIC-NEVPT2 with DLPNO
                           # DLPNO requires: trafostep RI and an aux basis
end

* xyz 0 1
N       0.0     0.0     0.0
N       0.0     0.0     1.09768
*

```

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

### Basic QM/QM2/MM Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/multiscalesimulations/qmmm-molecules.md.txt

An example configuration for a QM/QM2/MM calculation, specifying the ORCA functional, basis sets, MM force field file, and the atom lists for QM, QM2, and active regions.

```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
```

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

### Basic MOL-CRYSTAL-QMMM Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/multiscalesimulations/qmmm-crystal.md.txt

An example of a basic MOL-CRYSTAL-QMMM calculation, specifying the QM/MM method, DFT functional, basis set, optimization, frequency calculation, QM atoms, and active atoms, along with the input XYZ file.

```orcainput
! MOL-CRYSTAL-QMMM
! PBE def2-SVP Opt NumFreq
%qmmm
 NUnitCellAtoms 13
 QMAtoms {221:233} end                   
 ActiveAtoms {221:233} end  
end
*xyzfile 0 1 Ala_SC.xyz

```

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

### Automated QM/Active Region Setup with Fragmentation

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/multiscalesimulations/qmmm-general.md.txt

Use the QMMMSetup keyword and fragmentation procedures to automatically determine QM and active regions based on core atoms and system topology. This example uses RNA and ligand-specific fragmentation.

```orca
! QM/XTB
! QMMMSetup # just do the preparation and stop
%qmmm
 QMCoreAtoms {2032} end
 ActiveCoreAtoms {2032} end
 frag
   FragProc NABackbone, NASideChains, FunctionalGroups, Extend, Connectivity
 end
end

*xyz 0 1

```

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

### Install OPI from GitHub

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/workflowsautomatization/orcapythoninterface.html

Install OPI by cloning the GitHub repository and setting up a virtual environment. This method allows for direct access to the source code and development versions.

```bash
git clone https://github.com/faccts/opi.git
cd opi
python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install .

```

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

### For Loop Example

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/workflowsautomatization/compounddetails.md.txt

Demonstrates a 'For' loop for repetitive tasks. The loop variable iterates from a start value to an end value, inclusive. Both start and end values must be integers.

```orca
For i From 1 To 10 Do
  ! commands
EndFor;
```

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

### Demonstrate GoTo Command

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/workflowsautomatization/compound_examples.md.txt

This example demonstrates the usage of the GoTo command within Compound workflows.

```orca
%compound
  GoTo "step2"
%end

step1
  ! Some calculation
  RUNTYP HF
  %pal
    nprocs 8
  end
  * xyz 0 1
   H 0 0 0
  *

step2
  ! Another calculation
  RUNTYP SP
  %pal
    nprocs 8
  end
  * xyz 0 1
   H 0 0 1
  *

```

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

### ORCA Comment Example

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/essentialelements/input.md.txt

Illustrates how to add single-line comments in an ORCA input file, starting with '#'.

```orca
# This is a comment. Continues until the end of the line

```

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

### Example Basis Set File Format (3-21GSP)

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/essentialelements/basisset.md.txt

This is an example of the file format for defining a basis set, compatible with GAMESS-US. Lines starting with '!' or '#' are comments. Element symbols and shell types (S, L) are used.

```text
!                         lines in the beginning with '!' or '#' are comments
! BASIS="3-21GSP"
!Elements                             References                                
!--------                             ----------                                
! H - Ne: A.V. Mitin, G. Hirsch, R. J. Buenker, Chem. Phys. Lett. 259, 151 (1996)
! Na - Ar: A.V. Mitin, G. Hirsch, R. J. Buenker, J. Comp. Chem. 18, 1200 (1997). 
!
$DATA        ! Optional
HYDROGEN     ! (3s) -> [2s]      Element symbols are also recognized
 S   2
  1           4.50036231         0.15631167
  2           0.68128924         0.90466909
 S   1
  1           0.15137639         1.00000000
CARBON       ! (6s,3p) -> [3s,2p]                                
 S   3
  1         499.24042249         0.03330322
  2          75.25419194         0.23617745
  3          16.86538669         0.81336259
 L   2       ! L shells are a s and a p shell with identical exponents
  1           0.89739483         0.24008573         0.46214684
  2           0.21746772         0.81603757         0.66529098
 L   1
  1           4.52660451         1.00000000         1.00000000
$END         ! Optional
```

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

### LED Example Input

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/spectroscopyproperties/led.html

Example input file for analyzing the interaction of H2O with CH2 using the LED framework with PBE0-D3/def2-TZVP.

```input
! dlpno-ccsd(t) cc-pvdz cc-pvdz/c cc-pvtz/jk rijk verytightscf TightPNO LED

*xyz 0 1
  C(1)      0.16044643459993      0.10093183177121      0.22603351276210
  H(1)      1.04516129053973     -0.06834886965353     -0.41865951747519
  H(1)     -0.12579332868173      1.14737893892114      0.00305818518771
  O(2)     -1.48285705560792     -1.31933824653169      2.29891474420047
  H(2)     -0.91417368674145     -0.93085192992263      1.60917234463506
  H(2)     -1.15648922489703     -2.21246650333085      2.42094328175662
*


```

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

### CIM-DLPNO-CCSD(T) Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/modelchemistries/mdci.md.txt

Example configuration for performing a CIM-DLPNO-CCSD(T) calculation. Specifies the DLPNO-CCSD(T) method and basis sets.

```orcainput
#
# CIM-DLPNO-CCSD calculation
#
! DLPNO-CCSD(T) cc-pVDZ  cc-pVDZ/C CIM
* xyzfile 0 1 CIM.xyz

```

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

### Comprehensive ORCA Configuration Example

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/utilitiesvisualization/orca_2json.html

An example configuration file enabling basis set information and specific integrals, requesting all densities, and setting output formats to ASCII JSON and binary JSON.

```json
{
	"MOCoefficients": false,
	"Basisset": true,
	"1elPropertyIntegrals": ["dipole", "quadrupole", "velocity", "printLinMom", "angular_momentum", "higherMoment", "soc"],
	"1elPropertyRelIntegrals": ["dipole", "quadrupole", "angular_momentum", "soc"],
	"1elIntegrals": ["H", "S", "T", "V", "HMO"],
	"1elIntegralsRel": ["H", "S", "T", "V", "HMO"],
        "FockMatrix": ["F", "J", "K", "VXC", "Vsol"],
	"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"]
}
```

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

### Compound GoTo Example for ON/OFF Switch

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/workflowsautomatization/compound_examples.html

This script demonstrates the GoTo command in Compound to create an efficient ON/OFF switch. It uses conditional logic to navigate between 'turnOff' and 'turnOn' labels, toggling a switch variable and printing its state. The loop continues until a maximum iteration count is reached.

```Compound
# Compound Example on GoTo usage
# Efficient ON/OFF switch

%Compound
  Variable switch="OFF";
  Variable turnOff, turnOn, loopEnd;
  Variable maxIter = 10;
  for i from 0 to maxIter do
    if (switch="ON") then
      GoTo turnOff;
    else
      GoTo turnOn;
    endIf
    turnOff:
      print("Switch: %s\n", switch);
      switch="OFF";
      GoTo loopEnd;
    turnON:
      print("Switch: %s\n", switch);
      switch="ON";
      GoTo loopEnd;
    loopEnd:
  EndFor
End

```

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

### Initial LED Analysis Setup

Source: https://www.faccts.de/docs/orca/6.1/tutorials/prop/led.html

This snippet shows the input file configuration for an initial LED analysis. It specifies the calculation method, basis sets, and the 'LED' keyword to enable the decomposition. Fragments are defined using the '*XYZ' block.

```input
!DLPNO-CCSD(T) DEF2-SVP DEF2-SVP/C DEF2/J RIJCOSX VERYTIGHTSCF TIGHTPNO LED

*XYZ 0 1
C(1) -4.46463 -0.12110 0.22162
[...]
O(1) -0.99391 0.49487 -2.78478
C(2) 0.15487 -0.43421 0.93360
[...]
H(2) 5.37983 -0.86517 1.10337
*


```

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

### Example ORCA Property Block

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/utilitiesvisualization/property_file.md.txt

Demonstrates a typical property block starting with '$' and ending with '$End', containing various components.

```orca
$SCF_Nuc_Gradient
   &GeometryIndex 1
   &NAtoms [&Type "Integer"] 2
   &gradNorm [&Type "Double"]       7.6940943132805237e-02
   &grad [&Type "ArrayOfDoubles", &Dim (6,1)]
                                                         0

0                                      6.7009699964043727e-10
1                                     -1.3755030800675890e-10
2                                      5.4405462640094826e-02
3                                     -6.7009699282161039e-10
4                                      1.3755031156980307e-10
5                                     -5.4405462640095381e-02
   &Method [&Type "String"] "SCF"
   &Level [&Type "String"] "Relaxed density"
   &Mult [&Type "Integer"] 1
   &State [&Type "Integer"] 0
   &Irrep [&Type "Integer"] 0
$End
```

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

### ORCA CCSD/CPCM Output Snippet

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/essentialelements/solvationmodels.md.txt

Example output from ORCA showing the selected CCSD/C-PCM scheme. This helps in verifying the calculation setup.

```text
--------------------------------------------------------------------------------
                             ORCA-MATRIX DRIVEN CI
--------------------------------------------------------------------------------

--------------------------------
AUTOMATIC CHOICE OF INCORE LEVEL
--------------------------------

Memory available                           ...   2000.00 MB
Memory needed for S+T                      ...      9.26 MB
Memory needed for J+K                      ...     18.57 MB
Memory needed for DIIS                     ...    129.61 MB
Memory needed for 3-ext                    ...     72.69 MB
Memory needed for 4-ext                    ...    486.14 MB
Memory needed for triples                  ...      0.00 MB
 -> Final InCoreLevel    ... 5

Wavefunction type
-----------------
Correlation treatment                      ...      CCSD
Single excitations                         ... ON
Orbital optimization                       ... OFF
Calculation of Lambda equations            ... ON
Calculation of Brueckner orbitals          ... OFF
Perturbative triple excitations            ... OFF
CPCM scheme                                ... PTE(S)
Calculation of F12 correction              ... OFF
```

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

### ORCA ArrayOfDoubles Component Example

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/utilitiesvisualization/property_file.html

Array components, like 'ArrayOfDoubles', specify dimensions and then present data in blocks, starting with column indices.

```text
   &dipoleTotal [&Type "ArrayOfDoubles", &Dim (3,1)] "Total"
                                                         0

0                                     -5.1716015643064861e-01
1                                      5.1774970936823518e-02
2                                      7.8324050140722279e-01


```

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

### Example ORCA Property Block

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/utilitiesvisualization/property_file.html

A typical property block starts with '$' followed by the property name and ends with '$End'. It contains components denoted by '&'.

```text
$SCF_Nuc_Gradient
   &GeometryIndex 1
   &NAtoms [&Type "Integer"] 2
   &gradNorm [&Type "Double"]       7.6940943132805237e-02
   &grad [&Type "ArrayOfDoubles", &Dim (6,1)]
                                                         0

0                                      6.7009699964043727e-10
1                                     -1.3755030800675890e-10
2                                      5.4405462640094826e-02
3                                     -6.7009699282161039e-10
4                                      1.3755031156980307e-10
5                                     -5.4405462640095381e-02
   &Method [&Type "String"] "SCF"
   &Level [&Type "String"] "Relaxed density"
   &Mult [&Type "Integer"] 1
   &State [&Type "Integer"] 0
   &Irrep [&Type "Integer"] 0
$End

```

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

### CI Setup and Solution Block

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/utilitiesvisualization/utilities.html

This block shows the process of defining CI spaces and setting up the CI problem. It includes checks for multiplicity, number of configurations, CSF's, and roots, followed by the actual CI setup.

```text
=> Defining the CI spaces and setting up the CI             ...
==============================================================================
                             CI SETUP AND SOLUTION BLOCK
==============================================================================


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 
=============================================================================
                             CI SETUP AND SOLUTION BLOCK
=============================================================================


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

```

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

### Start UMA Server

Source: https://www.faccts.de/docs/orca/6.1/tutorials/workflows/extopt.html

Starts the UMA server for external model calculations. Ensure you are logged into HuggingFace and have access to the UMA repository.

```bash
oet_server uma

```

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

### QMMM Configuration Example

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/multiscalesimulations/qmmm-general.md.txt

Example of configuring QMMM calculations using various keywords within the %qmmm block. This includes settings for extending the active region, print levels, and nonbonded interactions.

```orca
!QMMM
%qmmm

# The extended active region, activeRegionExt, contains the atoms surrounding the 
# active atoms.
 ExtendActiveRegion distance  # rule to choose the atoms belonging 
                              # to activeRegionExt.
                              # no - do not use activeRegionExt atoms
                              # cov_bonds - add only atoms bonded covalently to 
                              # active atoms
                              # distance (default) - use a distance criterion (VDW 
                              # distance plus Dist_AtomsAroundOpt)
 Dist_AtomsAroundOpt 0.0      # in Angstrom (Default 0). Meaning only freeze atoms
                              # which touch the active atoms by their VDW spheres.
                              # only needed for ExtendActiveRegion distance
 OptRegion_FixedAtoms {27 1288:1290 4400} end  # manually define the
                                               # activeRegionExt atoms.
                                               # Default: empty list. 
                                               
# Printing options. All are true by default.
 PrintLevel 1               # Can be 0 to 4, 0=nothing, 1=normal, ...
 PrintOptRegion true        # Additionally print xyz and trj for opt region
 PrintOptRegionExt false    # Additionally print xyz and trj for extended 
                            # opt region
 PrintQMRegion true         # Additionally print xyz and trj for QM region
 PrintFullTRJ true          # Print trajectory of full system. Default true.
 PrintPDB true              # Additionally print pdb file for entire system, is 
                            # updated every iteration for optimization
 
# Computing MM nonbonded interactions within non-active region.
 Do_NB_For_Fixed_Fixed true # Compute MM-MM nonbonded interaction also for 
                            # non-active atom pairs. Default true.
# Treats all active water molecules that are treated on MM level as rigid bodies 
#  in optimization and MD simulation, see section "Rigid Water".
 Rigid_MM_Water false       #  Default false.

end
                         
*pdbfile 0 1 ubq.pdb  # structure input via pdb file, but also possible via 
                      # xyz file

```

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

### DLPNO-NEVPT2-F12 Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/modelchemistries/NEVPT2.html

Example input for a DLPNO-NEVPT2-F12 calculation, a linear scaling variant. The input structure is identical to NEVPT2-F12, with the exception of the DLPNO_NEVPT2 keyword.

```input
# aug-cc-pvdz/C used as RI basis
! cc-pvdz-F12 aug-cc-pvdz/C cc-pvdz-f12-cabs
%casscf nel 8
        norb 6
        mult 3,1

        # mandatory:
        TrafoStep RI           # RI approximation must be on for F12
        PTMethod DLPNO_NEVPT2  # DLPNO variant
        PTSettings
          F12 true             # request the F12 correction and CABS singles correction.
        end
end
*xyz 0 3
 O      0.0 0.0 0.0
 O      0.0 0.0 1.207
*

```

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

### Detailed LED Configuration in %mdci Block

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/spectroscopyproperties/led.html

This example demonstrates how to configure the Local Energy Decomposition (LED) using the %mdci block. It includes settings for the localization method (PipekMezey or FosterBoys), print level, maximum iterations, localization tolerance, skipping CCSD iterations, and decomposing the reference energy.

```input
%mdci
  LED 1               # localization method for the PNOs. Choices:
                      # 1 = PipekMezey 
                      # 2 = FosterBoys (default starting from ORCA 4.2)
  PrintLevel 3        # Selects large output for LED and prints the
                      # detailed contribution
                      # of each DLPNO-CCSD strong pair
  LocMaxIterLed 600   # Maximum number of localization iterations for PNOs
  LocTolLed     1e-6  # Absolute threshold for the localization procedure for PNOs
  Maxiter 0           # Skips the CCSD iterations and 
                      # the decomposition of the correlation energy
  DoLEDHF true        # Decomposes the reference energy in the LED part. 
                      # By default, it is set to true.
end

```

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

### Basic Input Block Structure

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/essentialelements/input.html

Input blocks in ORCA start with '%', followed by the block name and end with 'END'. This example shows a simple '%method' block.

```text
%method  
  method HF
END

```

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

### Define an ORCA Input Block

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/essentialelements/input.md.txt

Input blocks in ORCA start with '%', followed by the block name and end with 'END'. This example shows a basic '%method' block.

```orca
%method  
  method HF
END
```

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

### Open Shell LED Example Input File

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/spectroscopyproperties/led.md.txt

An example input file for an open shell DLPNO-CCSD(T) calculation using the LED scheme. The output is equivalent to the closed-shell case.

```orcainput
!
```

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

### Write2File Command Example

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/workflowsautomatization/compounddetails.md.txt

Demonstrates how to use the Write2File command to write formatted output to a file. Ensure the file is opened with OpenFile and closed with CloseFile.

```orca
! This is a comment

! Example for Write2File command
! First, open a file
OpenFile(my_output_file, "output.txt")

! Then, write formatted data to it
Write2File(my_output_file, "Hello, %s! The value is %f.\n", "World", 3.14159)

! Finally, close the file
CloseFile(my_output_file)
```

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

### Get Bond Distance Between Two Atoms

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/workflowsautomatization/compounddetails.md.txt

Returns the distance in Bohrs between two specified atoms within a geometry object. Atom indexing starts from zero.

```orca
!   GEOMETRY
    GetBondDistance(atomA=0, atomB=1)
!   END
```

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

### Basic sTD-DFT Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/spectroscopyproperties/tddft.md.txt

Invoke a standard sTD-DFT calculation by replacing 'Mode sTDA' with 'Mode sTDDFT'. This example uses the \omegaB97X functional with default parameters.

```orca
! wb97x def2-SVP tightscf smallprint printgap nopop 

%tddft
 Mode sTDDFT
 Ethresh 10.0
 axstda  0.56
 beta1  8.00
 beta2  0.00
 alpha1 4.58
 alpha2 0.00
end

*xyz 0 1 
  N     -1.726176    0.687742   -0.007335
  N      1.213763    0.735949   -0.027163
  N     -1.545188   -2.243058   -0.016803
  N      1.395005   -2.195166   -0.036972
  C      2.736733   -1.895646   -0.045209
  C      3.277248   -0.608637   -0.045175
  C      2.575908    0.605756   -0.036945
  C      0.977551    2.083559   -0.021690
  C     -0.288108    2.687287   -0.011220
  C     -1.529488    2.048274   -0.004419
  C     -3.067756    0.388045    0.001354
  H     -0.976948   -0.007843   -0.015911
  C     -3.608477   -0.899096    0.001258
  C     -2.907149   -2.113434   -0.007085
  C     -1.308388   -3.590806   -0.022331
  C     -0.042695   -4.194596   -0.032673
  C      1.198590   -3.555847   -0.039419
  H      0.645751   -1.499625   -0.028098
  C     -3.768181    1.641701    0.010433
  C     -2.832985    2.651061    0.006924
  C      2.228928    2.835679   -0.028158
  C      3.228183    1.912006   -0.037679
  C      3.437220   -3.149227   -0.053963
  C      2.502048   -4.158627   -0.050442
  C     -3.558669   -3.420017   -0.006390
  C     -2.559381   -4.343652   -0.015901
  H     -4.633051   -3.589818    0.000518
  H     -2.644718   -5.427990   -0.018393
  H     -0.016400   -5.285446   -0.035842
  H      2.681678   -5.229875   -0.055110
  H      4.519010   -3.247119   -0.061999
  H      4.366739   -0.548807   -0.052422
  H      2.314239    3.920088   -0.025633
  H      4.302487    2.081864   -0.044563
  H     -0.315062    3.778120   -0.007889
  H     -3.013895    3.722099    0.011827
  H     -4.849852    1.740964    0.018679
  H     -4.697992   -0.958441    0.008649
end
```

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

### Initial SINGLE_ANISO Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/spectroscopyproperties/single_aniso.html

This snippet shows the initial setup for a SINGLE_ANISO calculation, including relativistic effects for heavier elements and convergence smoothing. It generates an orbital file for subsequent steps.

```input
!DKH DKH-DEF2-SVP TightSCF conv Moread

%moinp "CeCOT2_1.gbw"

%basis
newgto Ce "SARC2-DKH-QZVP" end
end

%casscf nel 1
   norb 7  # 1 electrons in 7 f orbitals
   mult 2
   nroots 7  # 7 doublet states

   rel
     dosoc true  # include spin-orbit coupling
   end
end

*xyz -1 2
......
*

```

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

### Basic Command Syntax with Arguments

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/moleculardynamics/moldyn.md.txt

Illustrates the basic structure of commands with non-optional and optional arguments, showing valid ways to format them.

```orca
%md
  Command Arg1 Arg2 Arg3                  # fine
  Command Arg1, Arg2, Arg3                # fine
  Command Arg1 Arg2 Arg3 Optarg1          # fine
  Command Arg1 Arg2 Arg3 Optarg1 Optarg2  # fine
  Command Arg1 Arg2 Arg3 Optarg2          # will not work
end
```

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

### Compound Timer Usage Example

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/workflowsautomatization/compounddetails.html

Illustrates the declaration, start, stop, and total functions of a timer object in ORCA. Timers are used to measure execution time of code blocks.

```orca
# -----------------------------------------------
# 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 JSON Configuration File

Source: https://www.faccts.de/docs/orca/6.1/manual/_sources/contents/utilitiesvisualization/orca_2json.md.txt

An example configuration file demonstrating various keywords to enable/disable specific data exports, including basis set information and integrals.

```orca
{
	"MOCoefficients": false,
	"Basisset": true,
	"1elPropertyIntegrals": ["dipole", "quadrupole", "velocity", "printLinMom", "angular_momentum", "higherMoment", "soc"],
	"1elPropertyRelIntegrals": ["dipole", "quadrupole", "angular_momentum", "soc"],
	"1elIntegrals": ["H", "S", "T", "V", "HMO"],
	"1elIntegralsRel": ["H", "S", "T", "V", "HMO"],
        "FockMatrix": ["F", "J", "K", "VXC", "Vsol"],
	"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"],   <--- here you specify the names like "scfp" or "scfr" or all
	"JSONFormats": ["json", "bson"]
}
```

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

### Full Orca LFT Input for Nickel Complex

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/utilitiesvisualization/utilities.html

An example input file for orca_lft demonstrating the setup of a nickel complex with custom ligand field parameters and Slater-Condon parameters.

```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
    DOh = 1.2
    D1 = {-0.4*DOh}
    D2 = {0.6*DOh}
  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 + D2" # => dz2
    4   4 "1138.35 + D1" # => dxz
    5   5 "1138.35 + D1" # => dyz
    6   6 "1138.35 + D2" # => dx2-y2
    7   7 "1138.35 + D1" # => dxy
  end
  #--------------------

  #---SOC-CONSTANTS---
  #---All Values in eV---
  PARAMETERS
    ZETA_P = 11.341
    ZETA_D = 0.085
  end
  #--------------------

  #---SPECTRA/PROPERTIES---
  DoABS true
  Rel
    DoSOC true
  End
  #---------
End

*xyz 2 3
Ni 0.00 0.00 0.00
*

```

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

### NEVPT2-F12 Calculation Setup

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/modelchemistries/NEVPT2.html

Example input for an NEVPT2-F12 calculation. Requires an F12 basis, an F12-cabs basis, and a sufficiently large RI basis. The RI approximation must be enabled.

```input
# aug-cc-pvdz/C used as RI basis
! cc-pvdz-F12 aug-cc-pvdz/C cc-pvdz-f12-cabs
%casscf nel 8
        norb 6
        mult 3,1

        # mandatory:
        TrafoStep RI        # RI approximation must be on for F12
        PTMethod FIC_NEVPT2 # FIC-NEVPT2
        PTSettings
          F12 true    # request the F12 correction and CABS singles correction.
        end
end
*xyz 0 3
  O      0.0 0.0 0.0
  O      0.0 0.0 1.207
 *

```

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

### ORCA Startup Warnings Example

Source: https://www.faccts.de/docs/orca/6.1/manual/contents/quickstartguide/troubleshooting.html

This section displays typical startup warnings from ORCA. Pay close attention to these, as they can indicate potential issues or assumptions made by ORCA that might affect the calculation results. For restart operations, ensure the correct restart options are used.

```text
===========================================================================
                                   WARNINGS
                  Please study these warnings very carefully!
===========================================================================
WARNING: Geometry Optimization
  ===> : Switching off AutoStart
         For restart on a previous wavefunction, please use MOREAD


```
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