First-Principles Calculations of the Phonon, Elastic, and Thermoelectric Properties of a Ti2CO2 Monolayer.

The phonon, elastic, and thermoelectric properties of Ti2CO2 are investigated by first-principles calculations. The dynamic and mechanical stabilities of Ti2CO2 are confirmed. The Ti2CO2 monolayer exhibits strong acoustic-optical coupling with the lowest optical frequency of 122.83 cm-1. The TA mode originates from the contribution of Ti(XY) vibrations and has the largest gruneisen parameter at the Γ point; the LA mode has the main contribution of O(XY) and Ti(XY) vibrations and has the lowest gruneisen parameter at the M point. The analysis of the phonon spectrum indicates that the vibration contributions from C, O, and Ti atoms are mainly located in the low-, middle-, and high-energy regions, respectively. The Seebeck coefficient and electronic conductivity increase with increasing carrier concentration under room temperature. The analysis of mechanical properties shows that Ti2CO2 possesses a larger Young's modulus and bending modulus, which has a better ability to resist deformation. Thermal properties are further investigated.