Theoretical calculation for the equation of state and phase transition of lithium hydride crystal

Abstract

From the point of view of overlapping interactions between the nearest neighbours, while considering the compression effect of each ion, an ionic overlap-compression model is founded and applied to lithium hydride. The repulsive potential and cohesive energy curves of the crystal are calculated by a one-parameter variational method. The obtained equilibrium lattice constant (3.865 a₀), cohesive energy (? 218.82 kcal/mol), and bulk modulus (353 kbar) agree with experimental values surprisingly well. The calculated values of the equation of state also reach a good agreement with the experimental ones available below 40 kbar. A phase transition from NaCl to CsCl structure is predicted to occur around 0.85 Mbar, with a volume jump of about 6%.