Molecular orbitals and orbital energiesDESCRIPTION
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 hexacapole)
By default, Gaussian 98 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 Gaussian 98 semi-empirical calculations to the results of such other programs.
Note that the AIM keyword computes Atoms in Molecules-based atomic charges and performs other related analyses.
OPTIONS CONTROLLING OUTPUT FILE CONTENTS
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 virtual 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
and
densities. NaturalSpinOrbitals is a synonym for NOAB.
AlphaNatural
Do separate natural orbital analyses for the
and
densities, but store only the
densities for use in a .wfn file (see Output=WFN).
NOA is a synonym for AlphaNatural.
BetaNatural
Do separate natural orbital analyses for the
and
densities, but store only the
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
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 # IOP(4/5=8,4/38=-1) Guess=(Read,Save,Only) Geom=AllCheck
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 [120-121]. ESP and
MerzKollman are synonyms for MK.
CHelp
Produce charges fit to the electrostatic potential at
points selected according to the CHelp scheme [122].
CHelpG
Produce charges fit to the electrostatic potential at
points selected according to the CHelpG scheme [123].
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 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 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 [10,11,12,13,14,15,16,17].
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. Refer to the NBO documentation for
details on this input.
NBODel
Requests NBO analysis of the effects of deletion of
some interactions. Only possible at the Hartree-Fock level. 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
$.
RELATED KEYWORDS
Last Update: 02/16/2001