非简谐振动对SiC类石墨烯热输运性质的影响

Effect of non-harmonic vibration on thermal transport properties of SiC graphene

考虑到原子的非简谐振动,应用固体物理理论和方法,计算了SiC类石墨烯的简谐系数和非简谐系数,得到它的德拜温度、热容量和热导率等随温度的变化规律,探讨了原子非简谐振动对它的热输运性质的影响.结果表明:SiC类石墨烯的德拜温度随温度的升高而在117-126 K之间线性增大,定容比热随温度升高而非线性增大,热导率随温度升高而非线性减小,温度较低时变化较快,而温度较高时变化较慢,并随着温度升高而趋于常量;考虑到非简谐振动后,SiC类石墨烯的德拜温度、定容比热和热导率的值分别大于、小于和大于简谐近似的相应值,温度愈高,其差值愈大,即温度愈高,非简谐效应的影响愈显著;二维平面状的SiC类石墨烯的定容比热和热导率随温度的变化规律,与三维块状SiC晶体总体趋势相同,只是具体数值不同.

Considering the non-harmonic vibration of atoms,the simple harmonic coefficient and non-simple harmonic coefficient of SiC graphene are calculated by solid physics theory and method.The variations of Debye temperature,heat capacity and thermal conductivity with temperature are obtained.And the influence of atomic non-harmonic vibration on the heat transport properties is also discussed.The results indicate that the Debye temperature of SiC graphene increases linearly with the increase of temperature,in the temperature range of 117 K to 126 K.However,both the constant volume specific heat and thermal conductivity decrease nonlinearly with temperature rise,which are concretely expressed as rapidly changing when temperature is lower,then slowly changing when temperature is higher,and tends to be constant at last;After non-harmonic vibration,the data of Debye temperature,constant volume specific heat and thermal conductivity of SiC graphene are greater,smaller and greater than the corresponding simple harmonic approximation values,respectively.The higher the temperature,the greater the difference,that is,the more significant the influence of the non-harmonic effect;The constant volume specific heat and thermal conductivity of two-dimensional planar SiC graphene show the same change law with temperature as three-dimensional bulk SiC crystals,except different dimensions and specific values.