A quantum Monte Carlo study of the structural and electronic properties of small cationic and neutral lithium clusters.

Using the fixed-node diffusion quantum Monte Carlo method, we calculate the total energy of small cationic and neutral lithium clusters. We estimate the ionization potential, atomic binding energy, dissociation energy, and the second difference in energy. We present a critical analysis of the structural and electronic properties of the clusters. The bond lengths and binding and dissociation energies obtained from the calculations are in excellent agreement with the available experimental results. A comparative analysis of the dissociation energy and the second difference in energy indicates that the cationic clusters Li, Li, and Li are the most stable ones. We have also studied the electron correlation effects in the lithium clusters. The cationic clusters of odd-number size are relatively more favored in terms of correlation energy than their neighbors of even-number size. In the range of cluster sizes under investigation, we find that the contribution of electron correlation to ionization potential is not larger than 28% of its total values, whereas it enhances significantly the dissociation energy of the clusters reaching up to 70% of its total values for the most stable ones.