An interface exists to use the MRCC program of M. Kallay and J. Gauss within Molpro. The license and source code of the MRCC program must be obtained from Mihaly Kallay http://www.mrcc.hu/. Currently, only single reference methods with RHF reference functions are supported. Perturbative methods and CCn methods are only available for closed-shell. Furthermore, only serial execution is supported under Molpro, i.e. the mpp version cannot be used.
Please refer to the MRCC documentation on how to install the MRCC program. The MRCC executables must be found in PATH in order for Molpro to use them.
The MRCC program is invoked by the command
MRCC,options
directives
The available options summarized in options for MRCC 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 methods available in the MRCC program.
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.
| Option | Alias | Default value1) | Meaning |
|---|---|---|---|
METHOD | CALC | CC(n) | Computational method. See this section. |
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 | |
| Key | MRCC parameters | Notes | |
|---|---|---|---|
METHOD | LEVEL | ||
| 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 |
Closed-shell ground-state calculations for H2O:
***,mrcc calculations for h2o
gthresh,energy=1.d-8
geometry={
o;h1,o,r;h2,o,r,h1,theta}
theta=104
r=1 ang
basis=vdz
hf
mrcc,method=cc3; !CC3 calculation
method(1)=program
e(1)=energy !the final energy is returned in variable energy
ccsd(t) !CCSD(T) calculation using Molpro
method(2)='CCSD(T) (MOLPRO)'
e(2)=energy
mrcc,method=ccsd(t) !CCSD(T) calculation using MRCC
method(3)='CCSD(T) (MRCC)'
e(3)=energy
mrcc,method=ccsdt,dir=mrccdir !CCSDT calculation, run in directory mrccdir
method(4)=program
e(4)=energy
mrcc,method=ccsdt(q),restart=1,dir=mrccdir !CCSDT(Q) calculation
!restart with previous amplitudes
method(5)=program
e(5)=energy
mrcc,method=CC(n),excitation=4,restart=1,dir=mrccdir !CCSDTQ calculation
method(6)=program
e(6)=energy
table,method,e
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 excitation energies
gthresh,energy=1.d-8
geometry={
o;h1,o,r;h2,o,r,h1,theta}
theta=104
r=1 ang
basis=vdz
hf
ii=0
s=2 !number of states in each symmetry
do sym=1,4 !loop over irreps
ccsd;eom,-(s+0.1*sym);$p=molpro;save_energy
mrcc,method=ccsd, symm=sym,nstates=2;$p=mrcc;save_energy
mrcc,method=ccsdt,symm=sym,nstates=2;$p=mrcc;save_energy
s=1
enddo
{table,method,prog,states,e,exc
sort,3}
save_energy={ !procedure to save results in variables
!nogprint,variable
e1=energy(1)
do i=1,#energy
ii=ii+1
e(ii)=energy(i)
method(ii)=program
prog(ii)=p
states(ii)=i+0.1*sym
exc(ii)=(e(ii)-e1)*toev
end do
}
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 tests
gthresh,energy=1.d-8
geometry={o1;o2,o1,r1}
r1=2.2
set,state=1,symmetry=4,spin=2 ! Triplet sigma- state
basis=vdz
rhf
uccsd(t)
method(1)='UCCSD(T) MOLPRO'
e(1)=energy
rccsd(t)
method(2)='RCCSD(T) MOLPRO'
e(2)=energy
mrcc,method=ccsdt,dir=mrccdir
method(3)='CCSDT MRCC'
e(3)=energy
mrcc,method=ccsdtq,restart=1,dir=mrccdir
method(4)='CCSDT MRCC'
e(4)=energy
table,method,e
This yields
METHOD E UCCSD(T) MOLPRO -149.9815472 RCCSD(T) MOLPRO -149.9812566 CCSDT MRCC -149.9816705 CCSDT MRCC -149.9832255