Ab initio study of the lattice stability of β-SiC under intense laser irradiation

• The band gap of β-SiC vanishes and its metallic character is presented when Te > 6 eV.
• The TA modes of β-SiC are found to be negative Te = 3.39 eV.
• The LO–TO splitting degree of β-SiC at Γ point begin to decline as Te > 4.5 eV.
• The ionic strength of β-SiC is related to laser radiation intensity.

We have performed ab initio calculation of electronic properties, lattice-dynamical properties, charge density difference and charge density of β-SiC at different electronic temperatures (Te) using local density approximation (LDA) pseudopotential method within the density functional perturbation theory (DFPT). The results of electronic density of state display that β-SiC is still semiconductor with band gap of 1.51 eV at Te = 0 eV. But, beyond a temperature of 6 eV, the band gap of β-SiC vanishes and its metallic character is presented. The calculated phonon frequencies of β-SiC at Te = 0 eV show a good agreement with the experimental values and other calculations. However, when β-SiC undergoes a sharp increase of its electronic temperature, the phonon frequencies of β-SiC have a significant softening. The transverse acoustic modes of β-SiC are found to be negative Te = 3.39 eV which lead to the lattice instability. Moreover, the LO–TO splitting degree of β-SiC at Γ point increases at first and then reduces as Te is raised, the turning point is at Te = 4.5 eV. By using CUT3D, the results of the charge density difference and charge density of β-SiC indicate that when radiation intensity is only strong enough (e.g. Te > 4.5 eV), it will make the ionic strength of β-SiC weaken. Otherwise, when radiation intensity is not very high (e.g. 0–4.5 eV), the ionic strength of β-SiC will increase with the rise of Te.