标题： 电子、动态和超导性质的CaBeSi 显示英文标题

标题： Electronic, dynamical and superconducting properties of CaBeSi

摘要： 我们报告了在超导密度泛函理论（SCDFT）框架下对CaBe(x)Si(2-x)（x=1）的正常态和超导态的第一性原理计算。 CaBeSi与MgB2具有相同的结构和电子组成，这使得可以直接比较两种材料的电子性质、振动性质以及电子-声子相互作用。 尽管与MgB2有许多相似之处（例如费米能级处的sigma带和较大的费米面嵌套），但根据我们的计算，CaBeSi具有非常低的临界温度（Tc ~ 0.4 K，与实验结果一致）。 CaBeSi表现出复杂的能隙结构，在费米能级处有三个能隙：除了MgB2中也存在的两个sigma和pi能隙外，第三个能隙的出现与库仑排斥的各向异性有关，这种各向异性对成键和反成键的电子pi态产生不同的影响。 显示英文摘要

摘要： We report first-principles calculations on the normal and superconducting state of CaBe(x)Si(2-x) (x=1), in the framework of density functional theory for superconductors (SCDFT). CaBeSi is isostructural and isoelectronic to MgB2 and this makes possible a direct comparison of the electronic and vibrational properties and the electron-phonon interaction of the two materials. Despite the many similarities with MgB2 (e.g. sigma bands at the Fermi level and a larger Fermi surface nesting), according to our calculations CaBeSi has a very low critical temperature (Tc ~ 0.4 K, consistent with the experiment). CaBeSi exhibits a complex gap structure, with three gaps at Fermi level: besides the two sigma and pi gaps, present also in MgB2, the appearance of a third gap is related to the anisotropy of the Coulomb repulsion, acting in different way on the bonding and antibonding electronic pi states.