Ⅳ族FCC晶体基态结构和电子性质第一性原理研究

采用基于密度泛函理论的第一性原理方法,在广义梯度近似下,计算了Ⅳ族元素晶体的面心立方结构和电子性质.结果表明:Ⅳ族元素晶体的面心立方结构均可存在,面心立方结构Ge晶体的结合能最大,结构最稳定;面心立方结构C、Si、Ge和Sn的晶格常数分别为0.3509nm、0.4322nm、0.4225nm、0.4903nm,不随原子序数的增加而单调增加,是由面心立方锗晶体比面心立方硅晶体中电子云交叠小,产生的排斥较弱所导致的;面心立方结构C晶体是间接能隙为6.5e V的宽禁带半导体,面心立方结构Si晶体的导带和价带存在较小的交叠而呈现出半金属性,面心立方结构Ge和Sn的电子结构相似均表现为金属性,Ⅳ族元素面心立方结构晶体的电学性质由宽禁带半导体向金属转变.

First principles Study on structure and electronic properties of FCC crystals for group IV

Using the first-principles method based on the density functional theory (DFT), the structures and electronic properties of face-centered cubic (FCC) crystals for group IV were calculated with the generalized gradient approximation. The results show that there exists the FCC structures in these group IV crystals. The binding energy of FCC-Ge is the largest and most stable. The lattice parameters for FCC-C, -Si, -Ge and -Sn are respectively 0.3509nm, 0.4322nm,0.4225nm and 0.4903nm and does not increase monotonically with atomic number. The reason for leading to this phenomenon is the overlap of electron cloud which produces repulsive force for FCC-Ge is weaker than FCC-Si. The FCC-C with indirect band gaps of 6.5eV is wide band-gap semiconductor. FCC-Si is semimetal because the conduction and valence band have little overlap. The electronic structures for FCC-Ge and FCC-Sn are similar to each other and show metallic. Electrical properties of FCC crystals for group IV are changed from wide band-gap semiconductor to metal.