class TablePotential : public feasst::VisitModelInner
Represent isotropic interactions using a tabular potential that is precomputed and read from a file.
For an isotropic site, the radial distance, r, between the centers is scaled as \(z=[(r^\gamma - r_h^\gamma)/(r_c^\gamma - r_h^\gamma)]\) which varies from z=0 at the hard contact distance, r_h, to z=1 at the cutoff, r_c. A stretching parameter, \(\gamma\), increases the resolution at shorter distances when negative. This implementation is currently hard coded for \(\gamma=-2\) which avoids sqrt.
Interpolation uses Table1D::forward_difference_interpolation.
The format of the tabular potential stored in a file is as follows.
The first line should be ‘site_types’ followed by the number of site types and then the identity of each of those site types in order of the tables given below. (e.g., “site_types n i” where n is the number of site types and each following number is the type of each anisotropic site.)
There is a table for each unique pair of site types. For example, if the first line is as follows: “site_types 2 1 7” then the first table will be for interactions of site type 1 with site type 1 (i.e., 1-1), the second table will be for 1-7 interactions, and the third table will be for 7-7 interactions.
For each pair of site types, i <= j, a table is given by the following lines.
“inner [value]” is the inner hard cutoff distance.
”num_z [value]” is the number of energy values along the z parameter.
The last line is num_z space-separated values of the potential energy uniformly in the z range of [0, 1].