The investigation of the electronic and vibrational properties of some compounds within the density functional theory

We have investigated the structural, electronic and vibrational properties of LaAs and LaP compounds in the NaCl structure and the CsCl structure, LaN and LaSb compounds only in the NaCl structure by using General Gradient Approximation (GGA) of the density functional theory and ab-initio pseudopotentials. The calculated lattice constants of these six compounds are in good agreement with the available experimental and other theoretical results. These lattice constants and calculated electronic band structures have been used in the application of a linear response approach based on density functional perturbation theory for phonon studies. The calculated phonon spectra of LaSb are also in good agreement with available experimental data. The calculated phonon frequencies of LaAs and LaP compounds in the CsCl structure and LaN compound in the NaCl structure are unstable. Key Words : LaP, LaAs, LaN, LaSb, Density-functional theory, Electronic structure, Phonons