Simulation of Supercell Defect Structure and Transfer Phenomena in TlInTe2

Abstract

The local environment of atoms in a semiconductor compound TlInTe2 with tetragonal syngony is studied by the density functional theory (DFT). The introduction of a point defect (indium vacancies) into the TlInTe2 lattice is modeled using supercells. The DFT electronic properties (total and local partial densities of states (PDOS) of electrons) are modeled for the primitive TlInTe2 cell (16 atoms per unit cell) and for the defective TlInTe2 cell (where is the vacancy In) consisting of 32 atoms. The DFT-GGA calculations of the TlInTe2 band structure show that the band gap ( ) is = 1.21 eV. This value is significantly dif-ferent from the experimental value. The Hubbard model is used to correct the interaction of particles in the lattice. The DFT-GGA + U (U is the Hubbard potential) calculated by the TlInTe2 band gap is 0.97 eV. For the TlInTe2 supercell, the energies of the formation of a vacancy, the chemical potential of indium, and the standard enthalpy of the formation of TlInTe2 are calculated. When explaining the effect of various factors on the transport phenomena in TlInTe2, their thermal and electrical conductivity, both the DFT-calculated data and experimental data, are used. Taking into account the experimental data for the p-TlInTe2 crystals, the mechanism of conduction in the direction of structural chains (c axis of the crystal) is established. From the experimental data in the temperature range = 148–430 K, the band gap = 0.94 eV and the activation energy of impurity conduction = 0.1 eV (at 210–300 K) are estimated. At temperatures of ≤ 210 K, DC hopping conduction takes place in the p-TlInTe2 crystals. With this in mind, the following physical parameters are calculated for p-TlInTe2: the density of states localized near the Fermi level, their energy spread, and the average hopping distance.