非简谐振动和形变对ZnSe类石墨烯德拜温度热容量以及极性的影响

Influence of the anharmonic vibration and deformation on the Debye temperature heat capacity and polarity of graphene-like ZnSe

应用哈里森(Harrison)键联轨道法和固体物理理论和方法,考虑到原子的高阶非简谐振动,计算了ZnSe类石墨烯化合物的σ键和π键的极性、简谐系数和非简谐系数,得到它的德拜温度和定容热容量随温度变化的解析式以及形变引起的极性参量的改变量,探讨了形变对ZnSe类石墨烯极性的影响,并讨论了原子非简谐振动对化合物热力学性质的影响,结果表明:在300 K到1600 K温度区间内,简谐近似下,ZnSe的德拜温度为常量,热容量随着温度的升高呈非线性增大,其中温度较低时变化较快,温度较高时变化较慢并随着温度的升高而趋于常量.考虑到非简谐项后,德拜温度随着温度升高而增大,几乎为正比关系,而热容量的值比简谐近似的值有所减小,与第一非简谐项的影响相比,第二非简谐项的影响很小.形变对ZnSe类石墨烯的极性有重要的影响,在它的几种形变中,剪切形变对σ键的极性的影响最大,而键长形变对π键的极性的影响最小.温度愈高,非简谐效应愈显著.

This work uses Harrison bonding orbital method and solid physical theory to calculate the polarities ofσandπbonds,harmonic and anharmonic coefficients of ZnSe graphene-like compound on the consideration of high order anharmonic vibration of the atom.The Debye temperature,temperature-dependence analytical formula of heat capacity at constant volume,and change of polarity parameter caused by the deformation are therefore obtained,and the effect of deformation on the polarity of ZnSe class graphene and the influence of atomic anharmonic vibration on thermodynamic properties of compounds are discussed.The result shows that between300K to1600K temperatures,Debye temperature is constant under the harmonic approximation,heat capacity increases with the increase of temperature in a nonlinear way,it changed fast at low temperature,then changed slowly at high temperature,finally became constant with the increase of temperature.When non-simple harmonic term is considered,Debye temperature increases with the increase of temperature in a near proportional relation,the value of heat capacity reduces compared with that under the harmonic approximation.The research discloses that the second non-simple harmonic term has smaller influence compared with the first non-simple harmonic term.Therefore,the deformations have an important impact on polarity of ZnSe class graphene.Shear deformation has the greatest influence on polarity ofσbond,while bond length deformation has the smallest influence on polarity ofπbond.Anharmonic effect presents obviously with the increase of temperature.The higher is temperature,the more obvious anharmonic effect is presented.