Gradient of the First Order Reduced Density Matrix. A Look at two Charge-Shift Bonds

Abstract This article reports a generalization of the study of the 1-RDM cut along the bond axis for polyatomic molecules; the use of its gradient to partition 1-RDM maps into regions that are directly related to atomic orbital interactions. Gradient maps of various diatomics reveal insights that are not apparent in the 1-RDM or density maps. Studies of two charge-shift bonds show that although the two share common features, there are important differences that are not detected neither by density based analysis nor valence bond theory. The results suggest the gradient of 1-RDM as a valuable tool in bond analysis.