void p3dp_atom_pair_s(double *sj, double *si, double dxji[4]) { double ds[3]; V3SUB (sj, si, ds); V3ImagE (ds); V3M3LENGTH2 (ds, H, dxji); return; }
/* calculate dxji[]=x_j[]-x_i[] and |dxji|^2 */ void atom_pair (int j, int i, double dxji[4]) { double ds[3]; V3SUB (&s[DIMENSION*j], &s[DIMENSION*i], ds); V3ImagE (ds); V3M3LENGTH2 (ds, H, dxji); return; } /* end atom_pair() */