To specify a chosen operator matrix for a chosen operator OP in a chosen basis BAS, the input form is
For example, "MATRIX <FOCK/NBO>" specifies the Fock (or Kohn-Sham) matrix in the NBO basis, whereas "MATRIX <KINETIC/PNLMO>" specifies the kinetic energy matrix in the PNLMO basis.
To specify a chosen transformation matrix from one basis (BAS1) to another (BAS2), the input form is
For example, "MATRIX <AO/MO>" specifies the LCAO-MO transformation from basis AOs to MOs, whereas "MATRIX <NAO/NLMO>" specifies the LCNAO-NLMO transformation from NAOs to NLMOs.
In the above commands the chosen BAS name may be chosen from any of the twelve recognized basis sets:
The chosen OP name may be chosen from any 1e operator included in the input archive (.gen) file, such as
In addition, the SD (spin-density) operator is available for all open-shell NBO options.
Alternatively, OP might be any operator provided to NBO from the host ESS program through general ESS/NBO message-passing protocol. Check the ESS User Manual for valid OP options available in your host ESS program. Symbolic names or abbreviations for OP or BAS entries are generally case-insensitive.
A single MATRIX keyword may be followed by multiple (up to 25) bracket lists for different matrices, such as
"Old-style" keywords such as SPNBO or DINLMO are still recognized for some of these options, but many new possibilities become available in NBO 6.
The sample Gaussian I/O below illustrates requests for the Fock matrix in the NBO basis ("matrix <fock/nbo>") and the AO → NAO transformation matrix ("matrix <ao/nao>") for formamide. In each case the output format is similar to that for the respective "old-style" keywords FNBO, AONAO (which are still recognized in NBO 6).