MOLPRO

34 PROPERTIES AND EXPECTATION VALUES 261
34.3.2 Defining the density matrix (DENSITY)
DENSITY,record.file [,specifications]
Take density matrix to be analysed from record record on file file. Density matrices for specific
states can be selected using specifications, as explained in section 4.11. Note that the density
matrices are stored in the same record as the orbitals.
34.3.3 Populations of basis functions (INDIVIDUAL)
INDIVIDUAL;
34.3.4 Example
***,h2o population analysis
geometry={o;h1,o,r;h2,o,r,h1,theta} !Z-matrix geometry input
r=1 ang !bond length
theta=104
!bond angle
basis=6-311g**
hf
!do scf calculation
pop;
!Mulliken population analysis using mcscf density
individual
!give occupations of individual basis functions
http://www.molpro.net/info/current/examples/h2o_pop.com
If specified, the Mulliken populations of each individual basis function are printed.
34.4 Natural Bond Orbital Analysis
34.4.1 Calling the Natural Bond Orbital analysis program (NBO)
NBO,[WITH CORE=core option],[LEVEL=level],[KEEP WBI=wbi option];
The Natural Bond Orbital Analysis of Weinhold and coworkers (J. Chem. Phys. 83 (1985)
735, J. Chem. Phys. 83 (1985) 1736 and J. Chem. Phys. 78 (1983) 4066) can be called by
the use of the NBO card. It reads from a density or orbital record, and performs the necessary
transformations to Natural Atomic Orbitals (NAO), Natural Bond Orbitals (NBO) and Natural
Localized Molecular Orbitals (NLMO). The latter can also be saved to a record and later used
in local correlation treatments (cf. Section 29). By default, the full orbital space is used. The
core orbitals can, however, be left out of the procedure if core option=0.
One can choose to truncate the transformation series (e.g., only compute the NAO orbitals), with
help of the LEVEL keyword. If level=1, only the NAO transformation will be carried out. For
level=2 the NBO transformation is performed, and for 3 the NLMO (default).
Sometimes, the NBO procedure will not converge due to a bad ordering on the 2-center bond
search. The first run is based on the Wiberg bond index, but the algorithm switches to the atom
ordering on the subsequent runs. This can be avoided by the use of the option KEEP WBI. If
wbi option=1, the Wiberg bond index is used in all iterations.