Investigation of physical properties of some two dimensional crystals containing transition metals by Ab initio methods

In this study, the physical properties of some 2 dimensional crystals are investigated by using the density functional theory under different approaches. As a result of the calculations, the origins of the ultra low thermal conductivity of PbI2 compound were investigated and explained within the frame of the Slack theory. Studies on Mo2ScC2, Mo2ScC2T2 (T=O, F), and Mo2ScC2OH MXene compounds have shown that compounds are both mechanically and dynamically stable. Electronic band structure calculations have revealed that these compounds have metallic character. The results showed that Young's modulus of Mo2ScC2O2 compound was quite high. It was revealed that the Mo2ScC2OH compound has high Grüneisen parameter and negative coefficient of thermal expansion. It has been observed that Mo2ScC2 compound has high electronic transport coefficients. It has been determined that Mo2C compound is in an auxetic material. It has been understood that as a result of doping with Co atoms, the Mo2C compound gained magnetic properties, and its transport properties were significantly affected. The electronic and transport calculations on Mo2ScC2O2 showed that the metallic nature of this compound was preserved and such a defect did not significantly affect the electronic transport properties. The charge transfer dynamics of 1T-MoS2 and 2H-MoS2 compounds are studied and explained. Electronic and magnetic properties of NbSe2 compound were investigated and the results showed that the superconducting NbSe2 can also exhibit magnetic properties. Finally, it has been observed that 2D Cu2Te compound has semiconductor character, and its mechanical, thermal, and electronic transport properties are examined. The nature of its thermoelectric performance and lattice thermal conductivity is explained.