Improving approximate determination of the noninteracting electronic kinetic energy density from electron density

This work describes a new approach for approximate obtaining the positively defined electronic kinetic energy density (KED) from electron density. KED is presented as a sum of the Weizsacker KED, which is calculated in terms of electron density exactly, and unknown Pauli KED. The latter is presented via local Pauli potential and Gritsenko-van Leeuwen-Baerends kinetic response potential, to which the second-order gradient expansion is applied. The resulting expression for KED contains only one empirical parameter. The approach allowed to correctly reproduce all the features of KED, and electron localization descriptors as electron localization function and phase-space defined Fisher information density for main types of bonds in molecules and molecular crystals. It is also demonstrated that the method is immediately applicable to derivation of mentioned bonding descriptors from experimental electron density. Herewith the method is significantly free from the drawback of Kirzhnits approximation, which is now commonly accepted for evaluation of the electronic kinetic energy characteristics from precise X-ray diffraction experiment. (c) 2015 Wiley Periodicals, Inc.