next up previous contents index
Next: Options Up: Calculation of Molecular Structure Previous: Molecular Dynamics Calculations   Contents   Index

Counterpoise-Corrections using the JOBBSSE Script

The shell script jobbsse controls and executes the automatic calculation of the counterpoise correction as it has been formulated by Boys and Bernadi (S. F. Boys and F. Bernardi, Mol. Phys., 19, 553 (1970)) to estimate the Basis Set Superposition Error (BSSE). For a dimer, the cp-correction takes the form for the monomers A and B:

$\displaystyle E^{CP}_{AB} = E_{AB} - (E_{A(B)} - E_{A}) - (E_{B(A)} - E_{B}) $

Where parentheses denote ghost basis sets without electrons or nuclear charges. For a timer jobbsse used by default the conventional so-called site-site functional counterpoise corrections:

$\displaystyle E^{CP}_{ABC} = E_{ABC} - (E_{A(BC)} - E_{A}) - (E_{B(AC)} - E_{B}) - (E_{C(AB)} - E_{C})   .$

jobbsse works similar as the jobex script: it cycles through the SCF/DFT and, if needed, gradient and force relaxation programs and stops if either the maximum number of cycles is reached or the convergence criteria (change in the total energy, maximum norm of the gradient) are fulfilled. It does either only energy calculations or a full geometry optimization including up to three fragments. By default, the executable programs are taken from the load modules library within the TURBOMOLE directory.

Note that you need to set up the fragments (and possibly their symmetries using define in the geometry menu beforehand. The general structure of a jobbsse calculation is as follows:

  1. bsseenergy is invoked to generate input files for define, which is then used to prepare the control files (including occupation numbers, initial guess MOs, etc.) for the different ``ghost`` and monomer calculations and shell scripts with commands for calculations on these fragments.
  2. jobbsse cycles over the supermolecular complex and the fragments and computes the energies and, if requested, gradients for them. Then the counterpoise-corrected results are evaluated and written to the standard data groups ($energy and $grad).
  3. For geometry optimizations one of the structure relaxation codes (statpt or relax) is invoked to update the coordinates and check for convergence. If the structure optimization is not converged jobbsse continues with the previous step.
Note, that counterpoise-corrected calculations with jobbsse are NOT as black-box as ordinary geometry optimizations with jobex. The input generated for the fragments are based on the default occupation numbers obtained from the EHT guess, default assignments for the frozen orbitals, memory, etc. Since this might be different from what is needed (or even fail), it is recommended to let jobbsse stop after the initial setup step using the flag -setup and to check carefully the assigned basis sets, occupations number and subsystem symmetries. In particular, for MP2 or CC2 calculations with molecules containing not only the atoms H-Ar also the number of frozen orbitals should be checked, and if neccessary corrected.

next up previous contents index
Next: Options Up: Calculation of Molecular Structure Previous: Molecular Dynamics Calculations   Contents   Index