Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway.
J Chem Phys. 2012 Nov 21;137(19):194307. doi: 10.1063/1.4766360.
The electronic excitations of three noble-metall chains--copper, silver, and gold--have been investigated at the time-dependent density functional theory level. The reduced single-electron density matrix is propagated according to the Liouville-von Neumann equation in the real-time domain after an impulse excitation. The propagation in the real-time domain enables us to investigate the formation and size evolution of electronic excitations in these metallic chains with different number of atoms, up to a total of 26 atoms. The longitudinal oscillations at lower excitation energies are dominated by s → p transitions in these chains and have collective or central resonances, while the first peak involving d → p transitions in the longitudinal mode appears at a higher excitation energy and shows collective resonances. In the transverse oscillations, there are in most cases d → p transitions in each resonance, which can be attributed to either central or end resonances. Convergence of the oscillations, in particular those involving the collective and central resonances in the three noble-metal chains can only be observed for chains with 18 atoms or more. Different spectroscopic characteristics among these three metallic chains can be attributed to their different electronic structures, in particular the relativistic effects in the gold chains have a dramatic effect on their electronic structures and excitations.
我们在含时密度泛函理论水平上研究了三种贵金属链——铜、银和金的电子激发。在脉冲激发后，根据刘维尔-诺依曼方程在实时间域中传播约化单电子密度矩阵。在实时间域中的传播使我们能够研究这些具有不同原子数的金属链中电子激发的形成和大小演化，总共可达 26 个原子。在较低的激发能量下，纵向振荡主要由这些链中的 s → p 跃迁主导，并具有集体或中心共振，而在纵向模式中涉及 d → p 跃迁的第一个峰值出现在更高的激发能量，并显示出集体共振。在横向振荡中，大多数情况下每个共振中都有 d → p 跃迁，可以归因于中心或末端共振。只有在具有 18 个或更多原子的链中，才能观察到振荡的收敛，特别是那些涉及三种贵金属链中的集体和中心共振的收敛。这三种金属链之间的不同光谱特征可以归因于它们不同的电子结构，特别是金链中的相对论效应对其电子结构和激发有显著影响。
