How to compute the volume in CHARMM program?
Often times one needs to figure out the volume of the solute. Use command COORd VOLUme SPACe integer
integer - number of grid points for calculating the volume.
Since the explanations for VOLUme and SEARch commands in corman.doc are a little confusing, so let me paraphrase them here.
1) Fill scalar arrays sca1 and sca2 with RMIN and RMAX radii (you can first put them into WMAIn array and then copy to sca1 and sca2).
2) Compute the number of grid points.
Assuming a grid resolultion, say, 0.5 ang per grid, figure out the number of grids for each direction nx, ny, ny (compute first dX, dY or dZ for the molecule).
Multiply them together to get the total number of grid points.