形变和非简谐振动对SiC有效电荷和热膨胀系数以及弹性模量的影响

Effects of deformation and non-harmonic vibration on effective charge,thermal expansion and elastic modulus of SiC

应用哈里森(Harrison)键联轨道法和固体物理方法,考虑到形变和原子作非简谐振动,得到六角形二维类石墨烯AN-B8-N化合物的热膨胀系数、弹性模量以及有效电荷的解析表示式;以SiC为例,探讨了形变和原子非简谐振动对它们的影响.结果表明:SiC的热膨胀系数和弹性模量均随温度升高而缓慢增大,但变化较缓慢;若不考虑非简谐项,则SiC的热膨胀系数和弹性模量均为零,非简谐效应是SiC的热膨胀系数和弹性模量均随温度升高而增大的原因;形变会使SiC的正负离子的有效电荷的大小均减小,减小幅度分别为14.5%和8.56%,形变对正离子有效电荷的影响大于负离子.在所述的大小、剪切、轴向拉伸、原子振动形变这几种形变中,以轴向拉伸形变对有效电荷的影响最大,以大小形变和剪切形变的影响最小.温度愈高,原子的非简谐振动效应愈显著,形变对SiC的极性和有效电荷的影响愈大.

On the consideration of the deformation and atomic non-harmonic vibration, this paper applies the methods of Harrison bonding orbit and solid state physics to obtain thermal expansion coefficient and elastic modulus of hexagonal two-dimensional graphene compounds, and analytical formula of effective charge. Take SiC as an example, the paper discusses the effect of deformation and atomic non-harmonic vibration on SiC. The result shows that thermal expansion coefficient and elastic modulus of SiC enlarges slowly with increasing temperature, the thermal expansion coefficient and elastic modulus of SiC would be zero if not considering non-harmonic term, therefore, thermal expansion coefficient and elastic modulus enlarge with the increase of temperature is caused by non-harmonic effect. The deformation reduces the effective charge of SiC’s positive and negative ions by 14.5% and 8.56% respectively. The effect of deformation on positive ions is greater than negative ions. Among the deformations of size, shear, axial tensile and atomic vibrations, axial tensile deformation has the greatest effect on effective charge, while size deformation and shearing deformation has the smallest influence. When temperature increases, atomic non-harmonic vibration effect is presented more obvious, the deformation exerts greater influence on SiC polarity and effective charge.