Molcas Manual

https://molcas.gitlab.io/OpenMolcas/sphinx/
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The Molcas Manual documents Molcas, an _ab initio_ Quantum chemistry software package developed by a...
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### RLXRoot Keyword Example

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Example demonstrating the RLXRoot keyword in conjunction with CIRO or STAV for geometry optimization. This input specifies that CI root number 4 should be relaxed.

```Fortran
CIRoot= 3 5; 2 4 5; 1 1 3
RLXRoot= 4

```

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

### GASSCF Input Example

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

This example demonstrates the input structure for a GASSCF calculation, specifying active electrons, frozen orbitals, inactive orbitals, and the partitioning into three GAS spaces with specific electron counts and no inter-space excitations.

```input
&RASSCF
nActEl
 6 0 0
FROZEN
0 0 0 0 0 0 0 0
INACTIVE
2 0 0 0 2 0 0 0
GASScf
3
 1 0 0 0 1 0 0 0
2 2
 0 1 0 0 0 1 0 0
4 4
 0 0 1 0 0 0 1 0
6 6
DELEted
0 0 0 0 0 0 0 0


```

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

### Example of ALTEr Keyword Usage

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

This example demonstrates how to use the ALTEr keyword to interchange pairs of molecular orbitals within specified symmetry species and indices.

```text
ALTEr= 2; 1 4 5; 3 6 8
```

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

### GASSCF Calculation Example

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

An example input for a Generalized Active Space (GASSCF) calculation. It defines the number of active subspaces and specifies orbital counts and electron ranges for each subspace.

```input
GASSCF
 5
 2 0 0 0 2 0 0 0
 4 4
 0 2 0 0 0 2 0 0
 8 8
 0 0 2 0 0 0 2 0
 12 12
 0 0 0 1 0 0 0 1
 14 14
 4 2 2 1 4 2 2 1
 20 20
```

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

### SSCR Keyword Examples

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Examples demonstrating the usage of the SSCR keyword for computing spin correlation functions. The first example shows spin correlation from orbital 1 to 6, while the second example calculates spin correlation between sites A (orbitals 1-3) and C (orbitals 7-9).

```Fortran
* Spin correlation from orbital 1 to 6, i.e. local spin S_AB expectation value
* < S_AB > = S_AB (S_AB + 1)
SSCR = 6 1
* or
SSCR = 6
1 2 3 4 5 6
1 2 3 4 5 6
* Spin correlation between sites A (1-3) and C (7-9), i.e < S_A \cdot S_C >
SSCR = 3
1 2 3
7 8 9

```

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

### Minimal Input Example for State-Averaged Stochastic-CASSCF with RICD MC-PDFT

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

A basic input configuration demonstrating the integration of state-averaged Stochastic-CASSCF with RICD MC-PDFT. It includes gateway, seward, and rasrcf sections.

```input
&GATEWAY
 RICD
 COORD = coor.xyz
 BASIS = ANO-RCC-VTZP
 GROUP = full

&SEWARD

&RASSCF
 CIROOT = 2  2  1   * follows standard &RASSCF syntax
 NECI = ExNe
 NACTEL = 26 0 0
 INACTIVE = 20 17 17 14 0 0 0 0
 RAS2 = 0 0 0 0 7 6 6 5
 SYMMETRY = 1

>>foreach DFT in (T:PBE, T:BLYP, T:LSDA)

   &RASSCF
      FileOrb = $CurrDir/converged.RasOrb
      CIONLY
      FUNC = ROKS; $DFT
      NECI = ExNe
      NACTEL = 26 0 0
      INACTIVE = 20 17 17 14 0 0 0 0
      RAS2 = 0 0 0 0 7 6 6 5
      SYMMETRY = 1
>>enddo

```

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

### RFROOT Example for State-Averaged Density

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Specifies the generation of a reaction-field using the averaged density of S0 and S1 from a three-state averaged MCSCF calculation. Used with the PCM model.

```input
RFROOT = 3 3 ; 1 2 3 ; 1 1 0
```

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

### SUPSym Keyword Example

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Illustrates how to use the SUPSym keyword to restrict orbital rotations within specific symmetries, preventing symmetry-broken solutions. This is useful when the actual symmetry is higher than the input symmetry.

```text
SUPSym
2
   2 7 10; 2 8 11
0; 0; 0
```

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

### RASSCF Input for MC-PDFT Calculation

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Example input for running MC-PDFT calculations using the RASSCF program. It involves an initial CASSCF run followed by a second run with CI restart and ROKS functional.

```RASSCF
&RASSCF
Ras2
1 0 0 0 1 0 0 0

>>COPY $CurrDir/$Project.JobIph JOBOLD

&RASSCF
JOBIPH
CIRESTART
CIONLY
Ras2
1 0 0 0 1 0 0 0
FUNC
ROKS; T:PBE


```

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

### Define Initial Slater Determinant (DEFD)

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

This keyword is used to define an initial Slater determinant as a starting guess for FCIQMC dynamics. The program uses a list of occupied spin-orbitals sorted by symmetry.

```input
DEFD
  1 2 3 4 5 13 14 17 18 21 22 27 28 29 30 31 32 39 40 41 42 43 51 52 53 54 55 56 63 64 65 66

```

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

### RASSCF Input for HCI-CASSCF Calculation

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Example input for HCI-CASSCF calculation with the Dice–Molcas interface. Includes DICE, EPSIlons, DITErations, and DIOCuppy keywords.

```RASSCF
&RASSCF
Title= Water molecule. Active orbitals OH and OH* in both symmetries
Spin     = 1
Symmetry = 1
Inactive = 2 0 1 0
Ras2     = 2 2 0 0
THRS     = 1.0e-07 1.0e-03 1.0e-03
DICE
EPSIlons = 1.0d-4 1.0d-5
DITErations = 30
DIOCuppy
1
2 0  2 0


```

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

### RASSCF Input for DMRG-CASSCF Calculation

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Example input for DMRG-CASSCF calculation with the CheMPS2–Molcas interface. Includes DMRG specific keyword and 3RDM.

```RASSCF
&RASSCF
Title= Water molecule. Active orbitals OH and OH* in both symmetries
Spin     = 1
Symmetry = 1
Inactive = 2 0 1 0
Ras2     = 2 2 0 0
DMRG     = 500
3RDM


```

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

### RASSCF Input for Water Molecule Calculation

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Example input for RASSCF program for a water molecule calculation in C2v symmetry. Specifies active and inactive orbitals.

```RASSCF
&RASSCF
Title= Water molecule. Active orbitals OH and OH* in both symmetries
Spin     = 1
Symmetry = 1
Inactive = 2 0 1 0
Ras2     = 2 2 0 0


```

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

### RASSCF PRINT Keyword Example

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Sets the print levels for different sections of the RASSCF program. The numbers correspond to specific sections like Input, Transformation, CI, etc., with 0 being silent and 5 being debug.

```RASSCF
Print= 6 2 2 2 3 2 2 2 2

```

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

### Orbital-Free Embedding (OFE) RASSCF Example

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

This snippet demonstrates the input format for an Orbital-Free Embedding (OFE) RASSCF calculation. It requires specifying functionals for kinetic energy and exchange-correlation, with optional parameters for correlation potential fraction and decay factor, as well as energy convergence thresholds for freeze-and-thaw cycles.

```input
OFEMbedding
 ldtf/pbe
dFMD
 1.0   1.0d2
FTHAw
 1.0d-4

```

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

### Copying RDMs and Energy for NECI

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

A simplified command sequence to copy TwoRDM files to a working directory and echo the energy to a NEWCYCLE file. This is typically used after NECI simulation for state-averaged calculations.

```shell
cp TwoRDM_* /$YOUR_WORKDIR/
   echo $your_RDM_Energy > /$YOUR_WORKDIR/NEWCYCLE
```

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

### DIOCcupy Keyword Configuration

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Specifies the initial electronic configuration for HCI-CASSCF calculations. Requires the number of configurations followed by configuration strings.

```RASSCF
DIOCcupy
3
u u 2 0 2 0
2 0 u u 2 0
2 u d 0 u u

```

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

### XMSInter Keyword for XMS-PDFT

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Used in XMS-PDFT calculations to rotate states into XMS intermediate states. Generates rotation vector and intermediate Hamiltonian matrix files. Does not work with DMRG-optimized wave functions.

```input
XMSInter
```

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

### Input Permutation for Orbital Ordering (REOR)

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Allows the user to input a permutation for orbital ordering. It can specify the number of non-fixed point elements and their order, or use a flag to follow GAS space ordering.

```input
REOR
  3
  4 5 1

```

```input
REOR
  -1

```

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

### Shell Script for Renaming and Consolidating RDMs

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

This shell script automates the process of collecting reduced density matrices (RDMs) from different NECI calculation directories (e.g., doublet, quartet) and consolidating them into a working directory. It also extracts energy information and renames files to ensure correct ordering for state-averaged calculations.

```shell
export CALCBASE="location of your calculation"
export YOUR_WORKDIR="location of your scratch"

cd $CALCBASE/neci-doublet/  # contains roots 1 and 2
grep '*REDUCED' $YOUR_INPUT.out | awk '{ print $9 }' >> $CALCBASE/NEWCYCLE

cd $CALCBASE/neci-quartet/  # contains roots 3 to 6
grep '*REDUCED' mn3o4.out | awk '{ print $9 }' >> $CALCBASE/NEWCYCLE
# reverse order required, otherwise redundant rename
rename .4 .6 *.4; rename .3 .5 *.3 ; rename .2 .4 *.2; rename .1 .3 *.1

[for the other roots same procedure]

cd $CALCBASE
cp neci-doublet/run$1/TwoRDM_* neci-quartet/run$1/TwoRDM_* [other roots] $YOUR_WORKDIR
cp NEWCYCLE $YOUR_WORKDIR

```

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

### Copying Previous Calculation Job for RASSCF

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Copies a previous calculation's job file to be used as input for the RASSCF module. This is useful for reusing pre-optimized CI vectors or orbitals.

```bash
>>> COPY $WorkDir/$Project.JobIph JOBOLD

```

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

### CMSInter Keyword for CMS-PDFT

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Used in CMS-PDFT calculations to rotate states into CMS intermediate states. Generates rotation vector and intermediate Hamiltonian matrix files. Does not work with DMRG-optimized wave functions.

```input
CMSInter
```

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

### RASSCF Core Projection (CRPR) Option

Source: https://molcas.gitlab.io/OpenMolcas/sphinx/users.guide/programs/rasscf.html

Use the CRPR option to stabilize calculations involving states with core holes by projecting a specific orbital. This prevents orbital optimization from filling the core hole and ensures stability across geometry changes.

```input
CRPR
  1   33.0

```
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