Quantum Monte Carlo simulation for the many-body decomposition of the interaction energy and electron correlation of small superalkali lithium clusters

• Published in: The Journal of chemical physics Vol. 151; no. 1; p. 014303
• Main Authors: Brito, B G A, Hai, G-Q, Cândido, L
• Format: Journal Article
• Language: English
• Published: United States 07.07.2019
• ISSN: 1089-7690
• DOI: 10.1063/1.5099479

Using the fixed-node diffusion Monte Carlo (FN-DMC) method, we calculate the total energy of small lithium clusters Li (n = 2-6) to obtain the many-body decomposition of the interaction energy of 2- up to 6-body interactions. The obtained many-body decomposition of the interaction energy shows an alternating series with even and odd terms of attractive and repulsive contributions, respectively. The two-body attractive interactions guarantee the stability of the Li , Li , and Li clusters. For larger clusters Li and Li , the 4-body attractive interactions are required for their stabilization once the strength of the 3-body repulsive interactions overwhelms that of the 2-body attractive ones. With increasing the cluster size, the additive and nonadditive contributions to the interaction energy increase linearly in magnitude but with different slopes for the two-dimensional (2D) planar and three-dimensional (3D) cagelike clusters. The significant increment in nonadditive effects from the 4-atom to the 5-atom cluster has driven the structural transition from 2D to 3D. Combining the FN-DMC calculations with the Hartree-Fock many-body decomposition of the interaction energy, we extract the correlation effects, showing that an odd-even competition pattern in the many-body repulsive and attractive interactions is crucial for the stabilization of the clusters.