Plasmon dispersion and dynamic exchange - correlation potentials from two-pair excitations in degenerate plasmas
Plasmon dispersion and dynamic exchange - correlation potentials from two-pair excitations in degenerate plasmas
复制标题
简并等离子体中两对激发的等离子体色散和动态交换相关势
DOI：
10.1088/0953-8984/8/7/005
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
M. Tosi
中科院分区：
文献类型：
--
作者：
H. Böhm;S. Conti;M. Tosi
电子能量损失实验表明，一系列的碱金属的体等离子体分散体的快速软化。出于这些意见，我们重新考虑评估的动态，长波长的交换相关电位的电子流体，这是感兴趣的应用程序中的时间依赖的密度泛函理论。在等离子体频率下的值决定了交换相关对均匀电子流体中的领先等离子体色散系数的贡献。而插值方案最初提出的格罗斯和科恩假设单调增加的等离子体频率，我们研究的可能性，强烈的非单调行为所产生的等离子体激元和两对激发之间的共振过程。这一过程的评估与帮助下的总和规则和自洽性要求内的单极近似的介电函数。费米子等离子体和玻色子等离子体的情况下，平行处理和费米子等离子体在低耦合的结果的可靠性测试内的随机相位近似的介电函数的计算。在所有情况下，它被发现，共振过程中积累的振荡器的强度在附近，从而降低的值低于固定的压缩性总和规则的静态值。虽然这种降低本身不足以解释在低密度碱金属中测得的等离子体激元色散系数，但我们的结果为组合能带结构和交换相关计算提供了有用的输入。
Electron energy-loss experiments have shown a rapid softening of the bulk plasmon dispersion across the series of the alkali metals. Motivated by these observations, we reconsider the evaluation of the dynamic, long-wavelength exchange - correlation potential in the electron fluid, which is of interest for applications in time-dependent density functional theory. The value of at the plasma frequency determines the exchange - correlation contribution to the leading plasmon dispersion coefficient in the homogeneous electron fluid. Whereas an interpolation scheme originally proposed by Gross and Kohn assumes a monotonic increase of across the plasma frequency, we examine the possibility of strongly non-monotonic behaviour arising from a resonance process between plasmons and two-pair excitations. This process is evaluated with the help of sum rules and selfconsistency requirements within a single-pole approximation for the dielectric function. The cases of a fermion plasma and of a boson plasma are treated in parallel and the reliability of the results for the fermion plasma at low coupling is tested by calculations within a random-phase approximation for the dielectric function. In all cases it is found that the resonance process accumulates oscillator strength in the neighbourhood of , thus decreasing the value of below the static value fixed by the compressibility sum rule. Although this lowering does not suffice to account by itself for the measured plasmon dispersion coefficient in the low-density alkali metals, our results provide useful input for combined band-structure and exchange - correlation calculations.