This Appendix contains a more detailed description of the program pcksdisp. In the pEDI.X scripts, this program is used to calculate the CHF static and dynamic susceptibility functions of the monomers. In addition, both these objects can also be calculated at the UCHF level. The CHF and UCHF induction and dispersion energies are also reported. The uncoupled (UCHF) dispersion and induction energies are equivalent to E_{disp}^{(20)} and E_{ind}^{(20)} SAPT corrections, respectively. At the CHF level, the induction energy is equal to E_{ind,resp}^{(20)}. The CHF dispersion is equivalent to the so-called RPA dispersion (see Ref. 39 for examples). The RPA dispersion energy is currently not computed by the regular (non-parallel) SAPT algorithms. Two other quantities that can be obtained using pcksdisp are the static/dynamic dipole-dipole polarizability tensor and the isotropic C_{6} dispersion asymptotic coefficient (for the interaction of identical monomers), both at the UCHF and CHF levels.
The pcksdisp program uses the transformed intra- and intermonomer integrals (i.e., the MO representation) as generated by the ptran module. Therefore, within a script like pEDI.X, it should be run after the SCF and transformation programs. Note that currently pcksdisp assumes all integrals to be located in a single file f2e.000.001. Thus, all such files have to be properly merged after a parallel ptran run. This task is accomplished with the help of the program tmerge. To ensure that ptran generates all the integrals necessary for pcksdisp, the namelist INPUTCOR in the nameP.data file should contain the directives
The actual control parameters for pcksdisp are collected in the namelist INPUT, which should be appended to nameP.data (the scripts pEDI.X do this automatically) and look similar to
The meaning of the options is as follows:
The variable NQUAD sets the number of quadrature points to be used for the integration.