Theoretical investigation of some specific features of the electronic structure and optical properties of Benzoic Acid 2-Amino-4,6-Dimethylpyrimidine (1:1) co-crystals

Benzoic Acid 2-Amino-4,6-Dimethylpyrimidine (1:1) co-crystal have been comprehensively investigated by means of density functional theory. The electronic band structure show that the conduction band minimum (CBM) and the valence band maximum (VBM) are situated at the center of the Brillouin zone resulting in a direct band gap. Calculation were performed using the full potential linear augmented plane wave plus local orbitals (FPLAPW+lo) method in a scalar relativistic version as embodied in the WIEN2k code within the local density approximation (LDA), gradient approximation (PBE-GGA), Engel-Vosko generalized gradient approximation (EV-GGA) and the recently modified Becke-Johnson potential (mBJ). The calculated density of states explore that the VBM is mainly formed by N-p state while the CBM is formed by the strongly hybridized N-p and C-p states. There exists a strong hybridizations between C-s/p, H-s, N-s/p and O-s/p states above and below the Fermi level (EF). Which may led to covalent bonding between the states. To visualizes the charge transfer and the chemical bonding characters, the valence band's electronic charge density distribution were extensively investigated. The optical properties helps to get deep insight into the electronic structure therefore, details analysis to the calculated optical properties were performed. The optical properties confirm the existence of the band gap and the lossless regions.