Chaves Anderson S, Rondina Gustavo G, Piotrowski Maurício J, Tereshchuk Polina, Da Silva Juarez L F
São Carlos Institute of Physics, and ‡São Carlos Institute of Chemistry, University of São Paulo , 13560-970 São Carlos, São Paulo, Brazil.
J Phys Chem A. 2014 Nov 13;118(45):10813-21. doi: 10.1021/jp508220h. Epub 2014 Oct 29.
In general, because of the high computational demand, most theoretical studies addressing cationic and anionic clusters assume structural relaxation from the ground state neutral geometries. Such approach has its limits as some clusters could undergo a drastic structural deformation upon gaining or losing one electron. By engaging symmetry-unrestricted density functional calculations with an extensive search among various structures for each size and state of charge, we addressed the investigation of the technologically relevant Cu(n) and Pt(n) clusters for n = 2-14 atoms in the cationic, neutral, and anionic states to analyze the behavior of the structural, electronic, and energetic properties as a function of size and charge state. Moreover, we considered potentially high-energy isomers allowing foresight comparison with experimental results. Considering fixed cluster sizes, we found that distinct charge states lead to different structural geometries, revealing a clear tendency of decreasing average coordination as the electron density is increased. This behavior prompts significant changes in all considered properties, namely, energy gaps between occupied and unoccupied states, magnetic moment, detachment energy, ionization potential, center of gravity and "bandwidth" of occupied d-states, stability function, binding energy, electric dipole moment and sd hybridization. Furthermore, we identified a strong correlation between magic Pt clusters with peaks in sd hybridization index, allowing us to conclude that sd hybridization is one of the mechanisms for stabilization for Pt(n) clusters. Our results form a well-established basis upon which a deeper understanding of the stability and reactivity of metal clusters can be built, as well as the possibility to tune and exploit cluster properties as a function of size and charge.
一般来说，由于计算需求高，大多数研究阳离子和阴离子团簇的理论研究都假定从基态中性几何结构开始结构弛豫。这种方法有其局限性，因为一些团簇在获得或失去一个电子时可能会发生剧烈的结构变形。通过进行对称性不受限制的密度泛函计算，并对每个尺寸和电荷状态的各种结构进行广泛搜索，我们对技术上相关的Cu(n)和Pt(n)团簇进行了研究，其中n = 2 - 14个原子，涵盖阳离子、中性和阴离子状态，以分析结构、电子和能量性质随尺寸和电荷状态的变化行为。此外，我们考虑了潜在的高能异构体，以便与实验结果进行前瞻性比较。考虑到固定的团簇尺寸，我们发现不同的电荷状态会导致不同的结构几何形状，这表明随着电子密度增加，平均配位数有明显的降低趋势。这种行为促使所有考虑的性质发生显著变化，即占据态和未占据态之间的能隙、磁矩、脱离能、电离势、占据d态的重心和“带宽”、稳定性函数、结合能、电偶极矩和sd杂化。此外，我们发现具有sd杂化指数峰值的神奇Pt团簇之间存在很强相关性，这使我们能够得出结论，sd杂化是Pt(n)团簇稳定化的机制之一。我们的结果形成了一个坚实的基础，在此基础上可以更深入地理解金属团簇的稳定性和反应性，以及根据尺寸和电荷调节和利用团簇性质的可能性。
