SiC多型体几何结构与电子结构研究

采用平面波超软赝势法和范数不变赝势法对几种SiC多型体的几何结构、能带结构等进行了系统的研究.结果表明:6HSiC导带最低点在ML线上U点,用平面波超软赝势法计算时U点在(0000,0500,0176)点附近;而用范数不变赝势法计算时在导带最低点附近能带呈现不连续点,不连续点出现在(0000,0500,0178)点附近.两种赝势法计算结果相比,用平面波超软赝势法得到的导带最低点位置更靠近布里渊区M(0,05,0)点.在平面波超软赝势下,随着六角度的增加,cp,cpa增大的趋势较为明显,能隙和价带宽度变宽的趋势也较为明显.在计算极限内,绝对零度下4HSiC系统能量最低、最稳定,而Ewald能量显示3CSiC最稳定. 关键词： 密度泛函理论 电子结构 SiC

Studies on the geometric and electronic structures of SiC polytypes

By using the plane wave ultrasoft and norm conserving pseudopotential methods of density functional theory in the local density approximation, the lattice parameters and energy band structures of SiC polytypes are investigated. We found that the conduction band minimum in 6H SiC lies at U (0,0 500,0 176) point along the ML line in the Brillouin zone, according to the plane wave ultrasoft pseudopotential method. While the conduction band, according to the norm conserving pseudopotential method, displays discontinuity at (0,0 500,0 178) point along the ML line. The result obtained with plane wave ultrasoft pseudopotential method does not show any marked camel back, and its U point is closer to M (0,0 500,0) point than that with norm conserving pseudopotential method. The lattice parameters c/p, c/pa increase slightly with increasing hexagonality in the case of the plane wave ultrasoft pseudopotential method. The band gap and valence band width have the same trend. The calculated total energy of 4H SiC structure is the lowest in the four structures at zero temperature. However, the Ewald energy of the 3C SiC structure is the lowest among the polytypes.