高压下Al的零温电子结构和物态方程

 用LMTO法（线性Muffin-Tin轨道法），计算了金属铝的超高压电子结构及零温物态方程。Al的压缩比到10，压力达10 TPa。根据第一原理计算结果，在带结构方面，s带总是处于Fermi能以下，随着压力的增加，s、p和d的带宽增加，随后则杂化程度增加，所以s、d轨道的电子占据数连续变化。上述变化对压力的影响也是连续的，换言之，从s→d转变没有理由说明Al在0.5 TPa附近冲击Hugoniot的斜率的拐弯现象。而这一点则是与Altshuler的观点不同。物态方程的第一原理计算结果表明，bcc结构比fcc结构要软，但因差别不很大，即使发生fcc→bcc的转变，也不会引起Hugoniot的质的变化（拐弯）。Al的LMTO物态方程还表明，我们以前所采用的半经验的冷压误差可达30%。为此，根据LMTO结果，给出新的冷压表达式p=∑_i=0⁵a_iδ^i/3，δ=Ω₀/Ω，其中a₀=-7.327 79，a₁=18.754 3，a₂=10.209 7，a₃=-2.523 53，a₄=-4.787 2，a₅=6.065 94，拟合误差小于3%。

ELECTRONIC STRUCTURES ANDEQUATION OFSTATE FOR ALUMINIUM UNDER HIGH PRESSURE AT T=0K

The study for Al up to the pressure p=10 TPa, the compression Ω₀/Ω=10, by using the first principle calculations is performed. The energy band structures and electronic occupation numbers of the states for a series of lattice constants are presented. It follows from the energy band structures that s band always lies below the Fermi level. As the pressure increases, the bandwidths of s, p and d increase, and then the degree of hybridization become higher. So the electronic occupation numbers of s, d orbital change continuously. The effect of above mentioned changes to pressure is continuous too. In other words, s→d transition is not the reason for a break in the slope of the shock Hugoniot for Al near 0.5 TPa, as claimed by Altshuler. The equation of state at T=0 K shows that bcc structure is softer than fcc. The results calculated by LMTO are different from the semi-empirical ones given by us previously. A new correct fitting for EOS from the results of LMTO is presented.