基于密度泛函理论的第一性原理研究了四元Heusler合金Co2MnGe1-xGar和Co2FeGe1-xGax的晶体结构、半金属稳定性和磁性,发现随着掺入Ga比例x的改变,其晶格常数遵循Vigard原理.对于Co2 MnGal-x Gex系列的合金,其原胞磁矩很好地符合SP(Slater-Pauling)值和实验值；而对于Co2 MnGe1-xGax系列合金,其原胞磁矩虽然与实验值一致,但却随x的减小而逐渐偏离SP值.态密度显示,Co2 MnGe1-xGax系列合金在x=0～0.75的掺杂比例内都有0.4～0.6eV的自旋向下带带隙宽度,而Co2 FeGe1-xGax虽然在费米面附近也存在较高的自旋极化,但几乎不存在显著的自旋向下带带隙.此外,四元合金Co2 MnGe0.75 Ga0.25的费米面居于最小自旋带隙的中部,将具有较好的半金属稳定性.
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