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Electron correlation effects in ionic hydrogen clusters
Authors:P Bokes  I &#x;tich  L Mitas
Institution:P. Bokes,I. ?tich,L. Mitas
Abstract:We employ density functional, post‐Hartree–Fock, and quantum Monte Carlo methods to study the electronic structure, geometries, and behavior of positively charged Hm+ clusters with m=3,5,…,17. Their structure consists of a tightly bound H3+ core ion surrounded by successive solvation shells of H2 molecules. For the largest clusters, we propose new geometries. We find that correlated methods yield the stepwise decrease of enthalpies for dissociation of H2 from the clusters observed in experiments. Our best results are obtained by the diffusion Monte Carlo method, and by including finite temperature entropic effects, we are able to reproduce the experimental dissociation enthalpies with an unprecedented accuracy of less than 0.5 kcal/mol. These benchmark results contrast with erroneous predictions discovered in the density functional approaches. Finally, our analysis of the cluster energy surfaces indicates that under quantum and thermal fluctuations, the outer solvation shells will exhibit pronounced fluctional behavior. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 86–95, 2001
Keywords:hydrogen clusters  dissociation enthalpies  quantum Monte Carlo  correlated wave function  DMC  CISD  CCSD(T)  DFT
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