Romaniello P, de Boeij P L
Theoretical Chemistry, Materials Science Centre Rijksuniversiteit Groningen Nijenborgh 4, 9747 AG Groningen, The Netherlands.
J Chem Phys. 2005 Apr 22;122(16):164303. doi: 10.1063/1.1884985.
We included relativistic effects in the formulation of the time-dependent current-density-functional theory for the calculation of linear response properties of metals [P. Romaniello and P. L. de Boeij, Phys. Rev. B (to be published)]. We treat the dominant scalar-relativistic effects using the zeroth-order regular approximation in the ground-state density-functional theory calculations, as well as in the time-dependent response calculations. The results for the dielectric function of gold calculated in the spectral range of 0-10 eV are compared with experimental data reported in literature and recent ellipsometric measurements. As well known, relativistic effects strongly influence the color of gold. We find that the onset of interband transitions is shifted from around 3.5 eV, obtained in a nonrelativistic calculation, to around 1.9 eV when relativity is included. With the inclusion of the scalar-relativistic effects there is an overall improvement of both real and imaginary parts of the dielectric function over the nonrelativistic ones. Nevertheless some important features in the absorption spectrum are not well reproduced, but can be explained in terms of spin-orbit coupling effects. The remaining deviations are attributed to the underestimation of the interband gap (5d-6sp band gap) in the local-density approximation and to the use of the adiabatic local-density approximation in the response calculation.
我们在含时电流密度泛函理论的公式中纳入了相对论效应，用于计算金属的线性响应特性[P. 罗曼涅洛和P. L. 德博伊伊，《物理评论B》（待发表）]。在基态密度泛函理论计算以及含时响应计算中，我们使用零阶正则近似来处理主要的标量相对论效应。将在0 - 10 eV光谱范围内计算得到的金的介电函数结果与文献报道的实验数据以及近期的椭偏测量结果进行了比较。众所周知，相对论效应强烈影响金的颜色。我们发现，当纳入相对论时，带间跃迁的起始能量从非相对论计算得到的约3.5 eV 移至约1.9 eV。随着标量相对论效应的纳入，介电函数的实部和虚部相对于非相对论情况都有整体改善。然而，吸收光谱中的一些重要特征并未得到很好的再现，但可以用自旋轨道耦合效应来解释。其余的偏差归因于在局域密度近似中对带间能隙（5d - 6sp能隙）的低估以及在响应计算中使用了绝热局域密度近似。
