Some investigations on symmetry and external properties of molecular electron momentum densities

Abstract

It is known that the molecular electron momentum density γ (p) is inversion symmetric. In this article, the generalized repercussions of this fact on the symmetries of γ (p) are discussed. A comprehensive study of the symmetry transformation from positional to momentum density due to the introduction of inversion operator i in the symmetry point group of a molecular system (in r space) has been presented. The symmetry enhancement in C_3v and T_d point groups is brought out via the respective electron momentum density contour maps. Further, the extremal properties of γ(p) have been studied for CH₄, H₂O, HCN, NH₃, C₂H₂, C₂H₄, C₂H₆, and CO molecules. The local maxima are observed at p=0 and elsewhere, whereas the minima and saddle points are invariably found to be at p=0 for the molecules studied here.