FIRST-PRINCIPLES CALCULATION OF THE ELASTIC STIFFNESS TENSER OF ALUMINUM NITRIDE UNDER HIGH-PRESSURE

The first-principles method for calculating the elastic stiffness tenser of composite crystals has been given. Applying the present method to the wurtzite and rocksalt structures of AlN under normal and elevated pressure up to 25.8 GPa, we have determined the elastic stiffness tenser completely from first principles. The theoretical values for the wurtzite structure at normal pressure are in good agreement with the experimental ones given by Tsubouchi and Mikoshiba. The elastic stiffness constants have been evaluated from the total energies of the deformed static lattices. These energies have been calculated by using a calculation method based on the variational principle.