27.2 Running MRCC

The MRCC program is invoked by the command

MRCC,options
directives

The available options summarized in Table 10. For a detailed description please refer to the MRCC manual of M. Kallay (file ”manual” the mrcc directory)

In MOLPRO the method to be used can be given as a string (option METHOD=string). The available methods and the corresponding MRCC input parameters (see MRCC manual) as specified in Table 11.

Directives are usually not necessary, but the CORE, OCC, ORBITAL, MAXIT, directives work as in the MOLPRO CCSD program. In addition, the number of states can be given on a STATE directive and this has the same meaning as the EOM_NSTATES option.


Table 10: Options for MRCC
Option Alias Default value$^a$ Meaning
METHOD CALC CC(n) Computational method. See Table 11.
EXCITATION LEVEL -1 Excitation level in cluster operator
RESTART_CC RESTART 0 Restart option. If 1, restart with previous amplitudes.
DIRECTORY DIR '  ' Subdirectory in which MRCC runs
      (necessary for restart jobs)
EOM_NSING NSING -1 Number of excited singlet states in closed-shell case
EOM_NTRIP NTRIP 0 Number of excited triplet states in closed-shell case
EOM_NSTATES NDOUB -1 Number of states in open shell case.
SYMM SYMMETRY -1 Symmetry of excited states
DENSITY IDENS 0 Parameter for density calculation
HF   1 1 for canonical Hartree-Fock orbitals, 0 otherwise
SPATIAL   1 0 for spin-restricted orbitals, 1 for spin-unrestricted orbitals
NACTO   0 Number of active occupied orbitals
NACTV   0 Number of active virtual orbitals
SACC   0 Spin-adapted coupled cluster
DBOC   0 Diagonal BO correction
MEMORY   -1 Memory
TOL ENERGY -1.0 Energy convergence threshold
FREQ   0.0 Frequency for dynamic polarizabilities
FILE   fort Name for MRCC fortran files
CONVER ICONV 0 See mrcc manual
CS   1 See mrcc manual
DIAG   0 See mrcc manual
MAXEX   0 See mrcc manual
a) -1 means default value taken from MOLPRO


Table 11: Methods available in the MRCC program
    MRCC parameters  
  Key METHOD LEVEL Notes
CI(n) configuration interaction methods
  CISD 0 2  
  CISDT 0 3  
  CISDTQ 0 4  
  CI(N) 0 N Specify excitation level N using LEVEL
CC(N) coupled cluster methods
  CCSD 1 2  
  CCSDT 1 3  
  CCSDTQ 1 4  
  CC(N) 1 N Specify excitation level N using LEVEL
CC(N-1)[N] coupled cluster methods
  CCSD[T] 2 3  
  CCSDT[Q] 2 4  
  CC(N-1)[N] 2 N Specify excitation level N using LEVEL
CC(N-1)(N) coupled cluster methods. Also computes [n] corrections
  CCSD(T) 3 3  
  CCSDT(Q) 3 4  
  CC(N-1)(N) 3 N Specify excitation level N using LEVEL
CC(n-1)(n)_L methods (also computes (n) and [n] corrections)
  CCSD(T)_L 4 3  
  CCSDT(Q)_L 4 4  
  CC(N-1)(N)_L 4 N Specify excitation level N using LEVEL
CC(n)-1a methods
  CCSDT-1A 5 3  
  CCSDTQ-1A 5 4  
  CC(N)-1A 5 N Specify excitation level N using LEVEL
CC(n)-1b methods
  CCSDT-1B 6 3  
  CCSDTQ-1B 6 4  
  CC(N)-1B 6 N Specify excitation level N using LEVEL
CCn methods (only for ground states)
  CC3 7 3  
  CC4 7 4  
  CCN 7 N Specify excitation level N using LEVEL
CC(n)-3 methods
  CCSDT-3 8 3  
  CCSDTQ-3 8 4  
  CC(N)-3 8 N Specify excitation level N using LEVEL

Examples: Closed-shell ground-state calculations for H2O:

h2o_mrcc.com

This yields

 METHOD                 E
 CC3                -76.23912734
 CCSD(T) (MOLPRO)   -76.23905150
 CCSD(T) (MRCC)     -76.23905150
 CCSDT              -76.23922746
 CCSDT(Q)           -76.23976632
 CCSDTQ             -76.23973043

Excitation energies for H2O:

h2o_mrcc_eom.com

This yields

 METHOD   PROG    STATES       E             EXC
 CCSD     MOLPRO     1.1   -76.23580212    0.000
 CCSD     MRCC       1.1   -76.23580212    0.000
 CCSDT    MRCC       1.1   -76.23922746    0.000
 CCSD     MOLPRO     1.2   -76.23580212    0.000
 CCSD     MRCC       1.2   -76.23580212    0.000
 CCSDT    MRCC       1.2   -76.23922746    0.000
 CCSD     MOLPRO     1.3   -76.23580212    0.000
 CCSD     MRCC       1.3   -76.23580212    0.000
 CCSDT    MRCC       1.3   -76.23922746    0.000
 CCSD     MOLPRO     1.4   -76.23580212    0.000
 CCSD     MRCC       1.4   -76.23580212    0.000
 CCSDT    MRCC       1.4   -76.23922746    0.000
 CCSD     MOLPRO     2.1   -75.85033256   10.489
 CCSD     MRCC       2.1   -75.85033257   10.489
 CCSDT    MRCC       2.1   -75.85316687   10.505
 CCSD     MOLPRO     2.2   -75.95093334    7.752
 CCSD     MRCC       2.2   -75.95093335    7.752
 CCSDT    MRCC       2.2   -75.95299013    7.789
 CCSD     MOLPRO     2.3   -75.77630664   12.504
 CCSD     MRCC       2.3   -75.77630665   12.504
 CCSDT    MRCC       2.3   -75.77972816   12.504
 CCSD     MOLPRO     2.4   -75.87776149    9.743
 CCSD     MRCC       2.4   -75.87776150    9.743
 CCSDT    MRCC       2.4   -75.88051189    9.761

Open-shell ground-state calculations for O2:

o2_mrcc.com

This yields

 METHOD                 E
 UCCSD(T) MOLPRO   -149.9815472
 RCCSD(T) MOLPRO   -149.9812566
 CCSDT MRCC        -149.9816705
 CCSDT MRCC        -149.9832255

molpro@molpro.net 2018-10-21