9 Data for Conventional Table-CI Natural Orbitals

9.1 Natural Orbital Data - NATORB

The NATORB directive is used to request Natural Orbital (NO) generation, and comprises a single data line read to the variables TEXT, TEXTF and TEXTB using format (3A).

• TEXT should be set to the character string NATORB.
• TEXTF is an optional parameter that may be used to control the quantity of printed output produced by the module. Valid settings include the strings,
  • NOPRINT, to suppress the major part of the output from the module;
  • IPRINT, to produce an intermediate level of output. This option should be set to generate a print of the natural orbital coefficient array(s);
  • FPRINT, to produce output suitable for debugging purposes.
• TEXTB is an optional parameter that should be set to the string BYPASS if the user wishes to bypass NATORB processing. Such usage is typically associated with restarting Table-CI calculations.

9.2 Natural Orbital Data - CIVEC

The CIVEC directive is used to specify those eigenvectors of the CI-matrix to be analysed. The directive consists of a single data line with the character string CIVEC in the first data field. If natural orbitals associated with NVEC eigenvectors of the secular problem are to be generated, subsequent data fields should contain NVEC integers, the integers specifying the numbering of the CI-eigenvectors on the FORTRAN interface, FTN036, as generated by the DIAG sub-module. If the CIVEC directive is omitted under NATORB processing the natural orbitals of the first CI-vector will be generated.

Example

          CIVEC 1 3

The above data line may be used to generate natural orbitals from the first and third CI-eigenvector generated by the DIAG sub-module.

9.3 Natural Orbital Data - PUTQ

The PUTQ directive may be used to route spin-free natural orbitals to the Dumpfile, and consists of a single dataline with the first two fields read to variables TEXT, TYPE using format (2A).

• TEXT should be set to the character string PUTQ.
• TYPE should be set to one of the character strings AOS, A.O. or SABF, defining the basis representation required for the output NOs. The character string AOS and A.O. will yield the NOs in the basis function representation, suitable for subsequent input to the other analysis modules of GAMESS-UK. The string SABF will result in the NO expansion in the symmetry adapted basis representation, and should be used when performing iterative natural orbital calculations (see section 6.13 below)

The remaining data consists of a sequence of NVEC integers, (between 0 and 350 inclusive) specifying the section number of the Dumpfile where the spin-free NOs derived from the NVEC CI-vectors nominated by the CIVEC directive are to be placed.

Example

          PUTQ AOS 100 120

The spin-free NOs in the basis-set representation are output to sections 100 and 120 respectively of the Dumpfile. A section setting of 0 on the PUTQ directive will act to suppress natural orbital output to the Dumpfile.