Energetics, structure, and compressibility of NaF determined by the periodic Hartree–Fock method

Basis set development methods for molecular cluster calculations were used to develop basis sets for periodic ab initio calculations of the energy‐dependent properties of ionic crystals. Two extended, Gaussian basis sets for closed‐shell sodium and fluorine ions were developed to compare with two minimal basis sets in calculating the crystal structures, enthalpies of formation, and high‐pressure compression behavior of the B1 and B2 phases of NaF. Accurate calculation of the energy‐dependent properties to within experimental error required the use of the larger, extended basis sets. Enthalpies of formation for NaF–B1 at 0 K and 1 bar were calculated to be between −921 and −929 kJ/mol, which agrees well with an experimental value (−927±10 kJ/mol) estimated from calorimetric data. For the B1 phase, the zero‐pressure bulk modulus was calculated to be between 0.485 and 0.499 Mbar, as compared to the measured value of 0.464±0.062 Mbar. The calculated molar volume at zero pressure agrees to within 0.1% of the e...