Pauli potential and Pauli charge from experimental electron density

In this work, based on the experimental electron density, we present the approximate spatial distributions of the Pauli potential, one of the key quantities in the orbital-free density functional, for three crystalline systems: diamond, cubic boron nitride, and magnesium diboride. Our aim is to reveal a link between the Pauli potential and the orbital-free picture of chemical bond. We also expand the theoretical framework by developing the concept of the Pauli charge density. We find that both these quantities reproduce the electronic shell structure in the atomic core regions, while in the bonding region they reveal the different features for different bonding types, thereby distinguishing between ionic and covalent bond and also identifying the distinction between polar and nonpolar covalent bonds. Therefore, the Pauli potential and its associated charge density can be used as the orbital-free descriptors of chemical bond in the crystalline systems.