碳化硼、磷化硼与砷化硼的结构计算与热电性能研究

应用离散变分X_α量子化学分子轨道计算方法,研究了碳化硼、磷化硼和砷化硼在组成、结构、化学键和热电性能之间的关系,讨论了三种材料的同异之处。磷化硼和砷化硼虽然具有和碳化硼类似的结构,但是由于它们的P-P或As-As二原子链无双链特征,难以进行电子的传递;碳化硼的C-B-C或C-B-B三原子链上的键具有双键特征,有利于电子的传递及极化子的跃迁。因此,磷化硼和砷化硼无双键结构应该是其热电转换性能很差,以至被排除在热电材料之外的主要原因;而碳化硼的热电转换性能远优于磷化硼和砷化硼,具有双键特征应该是其主要原因。

STUDY ON STRUCTURES AND THERMOELECTRICPROPERTIES OF BORON CARBIDE,PHOSPHIDE AND ARSENIDE

The correlation among composition, structure, chemical bond and thermoelectric property of boron carbide, phosphide and arsenide is studied with SCF-DV-X_α method, one of calculation methods of molecular orbital in quantum chemistry. The differences between the three materials are studied. As the P-P and As-As chains have no characteristic of double bond, it is difficult for the boron phosphide and arsenide to transfer electrons, though they have the same structure as boron carbide. The C-B-C and C-B-B chains have the characteristic of double bond, so it is easy for the boron carbide to transfer electrons and hop the bipolarons. Therefore, boron phosphide and arsenide have no characteristic of double bond but boron carbide has, which is the main reason that as their thermoelectric property is too bad, boron phosphide and arsenide are not considered as the thermoelectric materials, but boron carbide has the much better thermoelectric property than boron phosphide and arsenide.