二元化合物内聚能的线性化缀加平面波能带方法的计算研究

采用线性化缀加平面波能带方法,研究了典型二元化合物NiAl,SiC,GaAs,MgS和NaCl的晶体总能和内聚能,着重考查了二元素Muffin-tin半径的选取对各晶体总能和内聚能的影响。计算结果表明,对NiAl合金,Muffin-tin半径的变动几乎不改变其晶体总能;组元原子的共价键半径可以作为共价键晶体如SiC和GaAs的Muffin-tin半径;但是,元素的离子半径不适合于作为具有较强离子键合的离子性晶体如MgS和NaCl的Muffin-tin半径,因为这时阳离子有较多的芯电子溢出Muffin-tin球。通过选取适当的Muffin-tin半径,对如上化合物计算得到的内聚能与实验结果符合。

LINEARIZED AUGMENTED PLANE-WAVE CALCULATION OF COHESIVE ENERGY OF BINARY COMPOUNDS

The total energy and cohesive energy of typical binary compounds, namely, NiAl, SiC, GaAs, MgS and NaCl, are studied by using he linearized augmented plane-wave method. Special emphasis is put on the effects of the choice of muffin-tin radii of the two elements. Results show that, for closely packed alloy NiAl, the variation of MT radius yields little change to the total energy; and the atomic covalent radii could be used in setting the MT radii for covalent crystals such as SiC and GaAs; but the ionic radii are not appropriate for crystals with strong ionic bonds such as MgS and NaCl due to a large number of core electrons lost out of the mufin-tin spheres of cations. The calculated cohesive energies with proper choice of muffin-tin radii are in good agreement with experimental results.