I would like to use the 2c-molecular-mean-field Hamiltonian (X2Cmmf) - what do i need to consider?ΒΆ

The 2c-molecular-mean-field Hamiltonian (X2Cmmf) is at present available for the following methods:

  • Coupled-Cluster
  • Fock-space Coupled Cluster (including the intermediate Hamiltonian version)

The remaining modules are not supported yet but patches are planned in the course of 2013:

  • KR-CI
  • TD-DFT

The X2Cmmf Hamiltonian scheme can be used for the Dirac-Coulomb as well as the Dirac-Coulomb-Gaunt Hamiltonian (add .GAUNT to **HAMILTONIAN).

As follows we will consider the necessary inputs for an X2Cmmf calculation where we perform the SCF + post-SCF calculation in one shot or two separate runs:

  • one-step procedure:
    • add .X2Cmmf to the **HAMILTONIAN keyword section:

that’s it. After the SCF calculation the program will proceed with the transformation to 2-components prior to the post-HF steps.

  • two-step procedure (EXPERT mode!):
  1. *SCF step*. Add .X2Cmmf to the **HAMILTONIAN keyword section:

and save the file DFCOEF (keyword –outcmo with our default submit script pam)

2. *post-HF step*. Remove .X2Cmmf from the **HAMILTONIAN section (non-intuitive (!) step which will be solved in Dirac12) and add the following keywords to the **MOLTRA and namelist RELCCSSD input section.

1 0 0 0
1 0 0 0

You are now ready to restart your post-HF calculation but do not forget to copy your MO-coefficient file DFCOEF to your scratch directory, i.e. add –incmo to your pam command line.