Electronic and optical properties of biphenylene under pressure: first-principles calculations

Structural parameters, electronic and optical properties of biphenylene have been investigated using the plane-wave ultrasoft pseudo-potential technique based on the first-principles density functional theory. The non-uniform pressure dependence of the lattice parameters may also mean that the biphenylene undergoes anisotropic compression. And the bulk modulus at ambient pressure and temperature is B-0 = 12.37 GPa and its derivative is B'(0) = 7.09. Meanwhile, the pressure dependence of the electronic band structure, density of states and partial density of states of biphenylene were presented. It is shown that biphenylene is a semiconductor with a direct gap of 2.325 eV, and a pressure induced decrease of the band gap is observed. Moreover, the complex dielectric function, absorption coefficient, reflectivity, refractive index and extinction coefficient are calculated and analysed. According to our work, we found that the optical properties of biphenylene undergo a red shift with increasing pressure.