新型双过渡金属MXene热电输运性能第一性原理计算

First principle calculation of thermoelectric transport performances of new dual transition metal MXene

二维双过渡金属MXene相较于单一过渡金属MXene,有着更高的可调控性,在热电器件方面有着潜在的应用.本文通过第一性原理的计算方法结合玻尔兹曼输运理论,研究了新型二维双过渡金属MXene单层TiZrCO_(2)和VYCO_(2)的稳定性和热电性能.结果表明,两者的热电输运性能优良.计算预测的结果:在最优载流子浓度下,300 K时,p型TiZrCO_(2)功率因子为11.40 mW/(m·K^(2)),远高于n型,p型VYCO_(2)功率因子(2.80 mW/(m·K^(2)))和n型(2.20 mW/(m·K^(2)))大小类似.300 K下,TiZrCO_(2)和VYCO_(2)的晶格热导率较低,分别为5.08 W/(m·K)和3.22 W/(m·K),并且随着温度升高进一步降低,900 K时为2.14 W/(m·K)和1.09 W/(m·K).TiZrCO_(2)和VYCO_(2)的热电优值随温度升高而增大,温度为900 K时,p型TiZrCO_(2)和VYCO_(2)的热电优值分别达到1.83和0.93,优于两者n型的0.23和0.84.双过渡金属MXene TiZrCO_(2)和VYCO_(2)相比单一过渡金属MXene(如Sc_(2)C(OH)_(2),ZT=0.5)具有更好的热电性能,有潜力作为综合性能优良的新型热电材料.本文采用的一套计算方法亦可为新型双过渡金属元素MXene热电性能探索提供一定借鉴.

The quantum restriction effect of charge carriers in two-dimensional materials can significantly improve their power factors.MXene,as a new type of two-dimensional double transition metal material,has attracted extensive attention due to thermoelectric properties,and higher controllability than single transition metal MXene,which has potential applications in thermoelectric devices.In this work,new two-dimensional monolayer double transition metal MXene,i.e.TiZrCO_(2)and VYCO_(2),are designed and their stabilities,electronic and thermoelectric properties are studied by the first principles and Boltzmann transport theory.It has been shown that both are indirect bandgap semiconductors with mechanical,thermodynamic and kinetic stability,and their thermoelectric properties(Seebeck coefficients,electrical and electronic thermal conductivities and lattice thermal conductivities)in a temperature range from 300 K to 900 K are studied.For the optimal carrier concentration at 300 K,the p-type TiZrCO_(2)power factor is 11.40 mW/(m·K^(2)),much higher than that of n-type one,and the VYCO_(2)power factor of p-type(2.80 mW/(m·K^(2)))and n-type(2.20 mW/(m·K^(2)))are similar to each other.At 300 K,TiZrCO_(2)and VYCO_(2)have low lattice thermal conductivities of 5.08 W/(m·K)and 3.22 W/(m·K),respectively,and the contributions of optical phonon to the lattice thermal conductivity are both about 30%,i.e.2.14 W/(m·K)and 1.09 W/(m·K)at 900 K,respectively.At the same time,it is found that at 300 K,when the material sizes of TiZrCO_(2)and VYCO_(2)are within 12.84 nm and 5.47 nm respectively,their lattice thermal conductivities are almost unchanged,and can be adjusted by adjusting the compositions.At 900 K,the thermoelectric value of p-type TiZrCO_(2)and VYCO_(2)reach 1.83 and 0.93,respectively,which are better than those of n-type,0.23 and 0.84.The double transition metals MXene TiZrCO_(2)and VYCO_(2)have better thermoelectric properties than the single transition metal MXene(such as Sc_(2)C(OH)_(2),ZT=0.5),and have the potential applications in new thermoelectric materials with excellent comprehensive properties.A set of calculation methods used in this paper can also provide some reference for exploring the thermoelectric properties of a new double transition metal element MXene.