Gaussian 03 Online Manual
Last update: 26 November 2007
Population
This properties keyword controls printing of molecular orbitals and several types of population analysis and atomic charge assignments. The default is to print just the total atomic charges and orbital energies, except for Guess=Only jobs, for which the default is Pop=Full (see below). Populations are done once for single-point calculations and at the first and last points of geometry optimizations.
The density that is used for the population analysis is controlled by the Density keyword. Note that only one density and method of charge fitting can be used in a job step. If several combinations are of interest, additional jobs steps can be added which specify Guess=Only Density=Check, to avoid repeating any costly calculations.
Population analysis results are given in the standard orientation.
Output controlled by the Pop keyword includes:
Molecular orbitals and orbital energies
Atomic charge distribution
Multipole moments: dipole through hexadecapole
By default, Gaussian prints molecular orbitals and performs population analyses regarding the MO coefficients from a semi-empirical calculation as coefficients of orthogonalized atomic orbitals (OAO's). There are important theoretical reasons for preferring this interpretation, but some other semi-empirical programs interpret these coefficients as referring to raw atomic orbitals. Use IOp(4/24=3) to compare orbitals from semi-empirical calculations to the results of such other programs.
APT charges are also computed by default during vibrational frequency calculations [586].
None
No orbitals are printed, and no population analysis is done.
Minimal
Total atomic charges and orbital energies are printed. This is the default for
all job types except Guess=Only.
Regular
The five highest occupied and five lowest virtual orbitals are printed, along
with the density matrices and a full (orbital by orbital and atom by atom) Mulliken
population analysis. Since the size of the output depends on the square of the
size of the molecule, it can become quite substantial for larger molecules.
Full
Same as the Regular population analysis, except that all orbitals
are printed.
BONDING ANALYSIS OPTION
Bonding
Do a bonding
population analysis in addition to the standard analysis. This is a Mulliken population
analysis in which only density terms involving pairs of basis functions on different
centers are retained. The other options control how much is printed.
NATURAL ORBITAL-RELATED OPTIONS
NaturalOrbitals
Do a natural orbital
analysis of the total density. NO is a synonym for NaturalOrbitals.
NOAB
Do separate natural orbital analyses for the α and β densities. NaturalSpinOrbitals
is a synonym for NOAB.
AlphaNatural
Do separate natural
orbital analyses for the α and β densities, but store only the α
densities for use in a .wfn file (see Output=WFN).
NOA is a synonym for AlphaNatural.
BetaNatural
Do separate natural orbital analyses for the α and β densities, but
store only the β densities for use in a .wfn file (see Output=WFN).
NOB is a synonym for BetaNatural.
SpinNatural
Generate
natural orbitals for the spin density (with α considered positive).
By default, natural orbitals are not included in the checkpoint file. Use a second job step of this form to place the natural orbitals into the checkpoint file:
--Link1-- %Chk=name # Guess=(Save,Only,NaturalOrbitals) Geom=AllCheck ChkBas
Run the formchk utility on the resulting checkpoint file to prepare the orbitals for visualization.
MK
Produce charges fit to the electrostatic potential at points selected according
to the Merz-Singh-Kollman scheme [216,217].
ESP and MerzKollman are synonyms for MK.
CHelp
Produce charges fit to the electrostatic potential at points selected according
to the CHelp scheme [218].
CHelpG
Produce charges fit to the electrostatic potential at points selected according
to the CHelpG scheme [219].
Dipole
When fitting charges to the potential, constrain them to reproduce the dipole
moment. ESPDipole is a synonym for Dipole.
AtomDipole
When fitting charges to the potential, also fit a point dipole at each atomic
center.
ReadRadii
Read in alternative radii (in Angstroms) for
each element for use in fitting potentials. These are read as pairs of atomic
symbol and radius, terminated by a blank line.
ReadAtRadii
Read
in alternative radii (in Angstroms) for each atom for use in fitting potentials.
These are read as pairs of atom number and radius, terminated by a blank line.
NBO-RELATED OPTIONS
NBO
Requests a full Natural Bond Orbital analysis, using
NBO version 3 [12,13,14,15,16,17,18,19].
NCS
Requests a partitioning of the NMR shielding tensors (computed using GIAOs) into magnetic contributions from bonds and lone pairs using the Natural Chemical Shielding Analysis of Bohmann et al. [582], which is based upon the NBO analysis method. By default, an analysis of the isotropic shielding is performed. NoNCS skips this analysis.
NCSDiag
Requests an NCS analysis of the diagonal tensor elements.
NCSAll
Requests an NCS analysis of all tensor components.
NPA
Requests just the Natural Population Analysis phase of NBO.
NBORead
Requests a full NBO analysis, with input controlling the analysis read from the
input stream. Use this option to specify keywords for NBO. Refer
to the NBO documentation for details on this input.
NBODel
Requests
NBO analysis of the effects of deletion of some interactions. Only possible with
SCF methods. Implies that NBO input will be read; refer to the NBO documentation
for details. Note that NBO input starts in column 2 so that the UNIX shell does
not interpret the initial $.
SaveNBOs
Save natural bond orbitals
in the checkpoint file (for later visualization).
SaveNLMOs
Save
natural localized molecular orbitals in the checkpoint file (for later visualization).
SaveMixed
Save the NBOs for the occupied orbitals and the NLMOs for the unoccupied orbitals
in the checkpoint file (for later visualization).
The following input file requests a bond order analysis using NBO 3:
# B3LYP/6-31G(d,p) Pop=NBORead
Example of NBO bond orders
0 1
C 0.000000 0.665676 0.000000
0.919278 1.237739 0.000000
H -0.919239 1.237787 0.000000
C 0.000000 -0.665676 0.000000
H -0.919278 -1.237739 0.000000
H 0.919239 -1.237787 0.000000
$nbo bndidx $end