chgm

Note

This command has been ported to the new APBS syntax (see YAML- and JSON-format input files):

• For finite difference, see finite_difference.FiniteDifference.charge_discretization() for more information.
• For finite element, see finite_element.FiniteElement.charge_discretization() for more information.

Specify the method by which the biomolecular point charges (i.e., Dirac delta functions) by which charges are mapped to the grid for a multigrid (mg-manual, mg-auto, mg-para) Poisson-Boltzmann calculation. As we are attempting to model delta functions, the support (domain) of these discretized charge distributions is always strongly dependent on the grid spacing. The syntax is:

chgm {flag}

flag is a text string that specifies the type of discretization:

spl0

Traditional trilinear interpolation (linear splines). The charge is mapped onto the nearest-neighbor grid points. Resulting potentials are very sensitive to grid spacing, length, and position.

spl2

Cubic B-spline discretization. The charge is mapped onto the nearest- and next-nearest-neighbor grid points. Resulting potentials are somewhat less sensitive (than spl0) to grid spacing, length, and position.

spl4

Quintic B-spline discretization. Similar to spl2, except the charge/multipole is additionally mapped to include next-next-nearest neighbors (125 grid points receive charge density).