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Be1-xMgxO合金的能带特性与相结构稳定性研究
Energy band properties and phase stability of Be1_xMgxO alloy
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摘要: 采用基于密度泛函理论的平面波赝势方法，对纤锌矿和岩盐矿结构Be1-xMgxO合金的晶格常数、能带特性和形成能进行计算，分析了不同Mg组分下不同结构的Be1-xMgxO合金晶格常数和能带差异．结果表明：随着Mg组分的增大，纤锌矿和岩盐矿Be1-xMgxO合金的晶格常数都线性增加，但它们的能隙都逐渐减小．对于相同Mg组分的Be1-xMgxO合金，岩盐矿结构的能隙要大于纤锌矿结构．当Mg组分为0．89时，Be1-xMgxO合金由纤锌矿相转变为岩盐矿相．为了使理论值与实验值相一致，对Be1-xMgxO合金的能隙计算值进行修正，得到纤锌矿和岩盐矿Be1-xMgxO合金的能隙弯曲系数b值分别为3．451eV和4．96eV．对纤锌矿BeO-MgO-ZnO三元合金的能隙和弯曲系数与晶格常数关系做了分析．Abstract: The lattice constants, energy band properties and phase stabilities of wurtzite (WZ) and rocksalt (RS)Be1-xMgxO alloys are investigated by the plan-wave pseudopotential method in the generalized gradient approximation based on the density functional theory. The theoretical results show that the lattice constants of WZ and RS Be1-xMgxO alloys increase and their bandgaps decrease as the content x of Mg increases from 0 to 1. For the same Mg content values, the bandgap of RS Be1-xMgxO alloy is greater than that of WZ Be1-xMgxO alloy. The WZ phase will transit to the RS phase when the Mg content is about 0.89. In order to obtain the theoretical values in accordance with the experimental results, the bandgaps of WZ and RS Be1-xMgxO alloys are corrected and the values of bandgap bowing parameter b are 3.451 eV and 4.96 eV for WZ Be1-xMgxO and RS Be1-xMgxO respectively. The reason of large band gap bowing parameter b is attributed to a large difference in ionic radius between Be and Mg. Besides, the relations among energy bandgap, bowing parameter and lattice constant of wurtzite BeO-ZnO-CdO ternary alloy are analyzed.
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