Effect of pressure on the structure and the electronic properties of LiCl[O.sub.4], NaCl[O.sub.4], KCl[O.sub.4], and N[H.sub.4]Cl[O.sub.4]

The effect of pressure on the structural and electronic properties of lithium, sodium, potassium, and ammonium perchlorates have been studied in terms of the density functional theory with allowance for the Van der Waals dispersion interaction. The pressure dependences of the geometric parameters, the band gaps, the densities of states, the charge distributions, and the atomic charges are calculated. The compressibilities of the perchlorates are found to be anisotropic, which is due to the differences of the lattice parameters and the nature of interatomic bonds. Ammonium cation is rotated under pressure around axis b at an angle of ~9[degrees]. The band gaps of the perchlorates are ~4.5-4.7 eV and increase with pressure.