This plugin reads "formatted ASCII" '.big' potential maps created by the format_phi utility, or the ASCIIPHI utility. To read the "unformatted" binary phi maps produced by DelPhi, use the grdplugin.

Notes:

Read-only
This plugin is used only to read files. VMD does not currently support writing this file type.

Grid Points
It is assumed that the density values of all files are arranged in a cubic grid.

Unit Cell
Since ASCII PHI maps do not explicitly state the angles of the basis vectors, it is assumed that they are orthogonal.