Abstract:
The effect of electron excitation plays an important role in ultrafast laser or fast ion irradiation. However, the existing knowledge on the fundamental properties of
γ−LiAlO
2 is limited and insufficient with regard to ultrafast irradiation. In this paper, we investigated the phonon spectrum, density of states and elastic modulus of
γ−LiAlO
2 at different electron temperature using the density functional perturbation theory (DFPT). The influence of electron excitation on the thermodynamic properties was calculated by quasi-harmonic approximation. From
Te=0 eV to 2 eV the elastic modulus, Debye temperature and melting temperature remain almost unchanged, in addition, the phonon frequency didn’t present negative value. Subsequently, the calculated band gad, Debye temperature and melting temperature decreased as the electronic temperature increased, but the phonon entropy revealed an inverse trend which confirm that the randomness of
γ−LiAlO
2 increases as the effect of electronic excitation is enhanced. Particularly, partial phonon frequencies begin to include imaginary frequencies, which signify the instability of the lattice at
Te=5 eV. At the same time, the band gap disappeared, and the elastic shear constants do not satisfy the Born stability criteria. It is shown that the electron excitation of 5 eV has a destructive damage to the
γ−LiAlO
2 crystal.