Integration Keywords¶
These keywords control the numerical integration grid used when the AOM is computed internally (i.e., when filedat is a fuzzy-partition keyword: mindefrho, netrho, becke, promrho).
They may also be given directly on the same line as the fuzzy keyword in Record 2. See Input Format — Record 2.
LEBEDEV nang¶
Number of angular grid points in the Lebedev quadrature used for the angular part of the fuzzy AOM integration. Default is 434.
Available Lebedev grid sizes are the standard Lebedev orders (e.g., 110, 194, 302, 434, 590, 770, …). Higher values increase accuracy at the cost of compute time.
NRAD nrad¶
Number of radial grid points in the Becke-type integration. Default is 100.
Higher values improve accuracy for atoms with steep density variations near the nucleus (heavy elements). Values of 200–400 are common for production calculations.
IRMESH irmesh¶
Selects the radial mapping function that transforms the \([0, \infty)\) range to the finite integration interval. Default is 1.
irmesh |
Mapping |
|---|---|
1 |
Becke mapping (default) |
2 |
Gauss-Chebyshev |
KPOWER pow¶
The iterative K parameter in Becke's fuzzy-cell partitioning scheme, controlling how sharply the weight function \(w_A\) transitions between atoms. Default is 3 (the standard value from Becke's original paper).
Higher values make the partition more step-like (sharper atom boundaries); lower values make it smoother.
Only relevant when filedat = becke.
RHOPOW rhopow¶
Exponent applied to each promolecular atomic density \(\rho_A\) when computing the weight:
Default is 1.0 (standard Hirshfeld / promolecular weights). Only relevant when filedat = promrho.
Inline integration parameters¶
For mindefrho, netrho, and becke, the integration parameters may be given directly on the filedat line in Record 2:
mindefrho NANG NRAD IRMESH
netrho NANG NRAD IRMESH
becke NANG NRAD IRMESH POW
These are equivalent to using the LEBEDEV, NRAD, IRMESH, and KPOWER keywords later in the input.