Evaluation of One-Electron Properties

Code author: Robert M. Parrish and Andrew C. Simmonett

Section author: Andrew C. Simmonett

PSI4 is capable of computing a number of one-electron properties summarized in the table below. The properties will be computed from the last computed one-particle density, using the following syntax:

oeprop("MO_EXTENTS", "MULTIPOLE(4)", title = "hello!")

The named argument, title, is completely optional and is prepended to any globals variables set during the computation. The unnamed arguments are the properties to be computed. These can appear in any order, and multiple properties may be requested, as in the example above. Note that, due to Python syntax restrictions, the title argument must appear after the list of properties to compute. The available properties are shown in the table below.

Current one-electron property capabilities of PSI4

Feature	Keyword	Notes
Electric dipole moment	DIPOLE
Electric quadrupole moment	QUADRUPOLE	Raw (traced) moments and traceless multipoles
All moments up order N	MULTIPOLE(N)	Only raw (traced) moments. Sets global variables e.g. “DIPOLE X”, “32-POLE XYYZZ”
Transition dipole moment	TRANSITION_DIPOLE
Transition quadrupole moment	TRANSITION_QUADRUPOLE
Electrostatic potential, at nuclei	ESP_AT_NUCLEI	Sets global variables “ESP AT CENTER n”, n = 1 to natoms
Molecular orbital extents	MO_EXTENTS
Mulliken atomic charges	MULLIKEN_CHARGES
Löwdin atomic charges	LOWDIN_CHARGES
Wiberg bond indices	WIBERG_LOWDIN_INDICES	Uses (Löwdin) symmetrically orthogonalized orbitals
Mayer bond indices	MAYER_INDICES
Natural orbital occupations	NO_OCCUPATIONS

Basic Keywords

Multipole moments may be computed at any origin, which is controlled by the global PROPERTIES_ORIGIN keyword. The keyword takes an array with the following possible values:

Allowed origin specifications

Keyword	Interpretation
[x, y, z]	Origin is at the coordinates, in the same units as the geometry specification
[“COM”]	Origin is at the center of mass
[“NUCLEAR_CHARGE”]	Origin is at the center of nuclear charge