中文摘要：

应用线性响应的线性糕模轨道方法计算AlB2型结构的新超导体CaAlSi的电子能带、声子谱及电子-声子耦合常数，并讨论了它们的超导电性．通过比较两种结构模型的计算结果可以看出：若CaAISi中Al，si原子沿c轴方向以-Al-Al-A1-,（或-Si-Si-Si-）排列，低频B1g模式的声子频率沿A-L方向出现虚频，使得这种结构处于不稳定状态，电子-声子耦合表现异常增大；若Al，si原子沿c轴方向以-Al-si-A1-排列，声子振动模式的增加消除了低频声子的异常软化,由此计算得到的声子对数平均频率增大为147K，电子-声子耦合常数A=0．80,用中等耦合强度的Bardeen-Cooper-Schrieffer理论可合理解释其超导电性。

英文摘要：

Using response-linearized linear muffin-tin orbital method we have studied the electronic band structure, phonon spectra, electron-phonon coupling and superconductivity of the new superconductor CaAISi with A1B2-type structure. The following conclusions are drawn from our calculations. （1） If A1 and Si atoms are assumed to be arranged along the c-axis in a long-range ordered （-A1-A1-A1- and -Si-Si-Si-） structure, one should obtain the uhrasoft B1g phonon mode and hence very strong electren-phonon coupling in CaAlSi. However, the appearance of imaginary frequency phonon modes indicates the instability of such a structure. （2） For A1 and Si atoms arranged along the c-axis in a long-range ordered （-A1-Si-A1-） structure, the calculated electren-phonon coupling constant is equal to λ=0.80 and logarithmically averaged frequency ωln is 147 K. This calculated result can correctly yield the superconduction transition temperature of CaAlSi by the standard Bardeen- Cooper-Schrieffer theory for moderate electren-phonon coupling strength.