ab initio calculations, a small refinement was made to the MMC electrical representation of HCN to improve the correspondence with the aug-ccpVTZ/MP2 results. This refinement was to distribute the dipole moment to two sites. Instead of a central dipole of 1.19537 a.u. at the mass center, a slightly larger value of 1.37537 a.u. was used at that site, and then in addition, an off-setting dipole of 0.18 a.u. was used at the C–H bond midpoint. The quadrupole and octupole moments were unchanged from their original values [20] and kept at the mass center.