高压下贵金属锂合金的超导电性研究

Study on superconductivity of noble metal lithium alloy under high pressure

自1921年首次发现超导体之后,其被广泛应用在超导计算机、电子学、医学影像等领域,成为百年以来物理学界研究的焦点.目前,低压超导体更是人们一直研发的重要材料.本文将铜元素与锂元素混合,在高压环境下进行系统的结构预测.利用第一性原理的计算方法,在50 GPa的压强下,得到了两种反常化学计量比的化合物Li_(4)Cu和Li_(6)Cu.观察发现,Li_(6)Cu晶体结构是以铜原子为中心、周围十二个锂原子构成的二十面体“Li_(12)Cu”,铜原子通过获得锂原子提供的大量电子,达到了较高的负氧化态(-3.5).另外,通过电声耦合计算,估算得到了Li_(4)Cu和Li_(6)Cu的超导转变温度T c分别为2.3 K和14.5 K.本研究证实了贵金属锂合金是潜在的超导电材料,为后续理论和实验的研究提供了借鉴.

Superconductors first discovered in 1921 have been widely used in superconducting computers,electronics and medical imaging and other fields,and have become the focus of physics research for a century.Currently,low-voltage superconductors are even more desirable materials.In this work,copper and lithium elements were mixed to predict the structure of the system under high pressure environment.Two compounds with abnormal stoichiometric ratios,Li_(4)Cu and Li_(6)Cu,were obtained at 50 GPa by using the first principles calculation.It is found that the crystal structure of Li_(6)Cu is an icosahedron“Li_(12)Cu”with copper atoms as the center and twelve lithium atoms around it.Copper atoms reach a high negative oxidation state(-3.5)by obtaining a large number of electrons provided by lithium atoms.In addition,the superconducting transition temperatures T c of Li_(4)Cu and Li_(6)Cu are estimated to be 2.3 K and 14.5 K by electroacoustic coupling calculation.This work confirms that noble metal lithium alloy is a potential superconducting material,which provides a reference for the subsequent theoretical and experimental research.