Theoretical calculation for the high pressure properties of alkali fluorides

The overlap repulsive potentials of ion pairs (Li + −F − , Na + −F − and K + −F − ) are calculated by means of generalized Heitler-London method and the numerical results are fitted in the Born-Mayer form, i.e. Dexp (-αR), Then the parameter D for each pair potential is modified to satisfy the crystal equilibrium condition at the experimentally known lattice constant. The redetermined repulsive potentials are applied to calculate the cohesive energies, bulk moduli, equations of state and NaC1-to-CsC1 structural phase transition pressures of LiF, NaF and KF crystals. The results obtained are compared with some other theoretical values and the available experimental data, and good agreement is reached.