Journal
PHYSICAL REVIEW B
Volume 82, Issue 8, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.82.081405
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Funding
- U.S. DOE Office of Science [DE-AC02-05CH11231, DE-AC05-00OR22725]
- U.S. DOE BES Division of Materials Sciences Engineering
- ORNL
- U.S. DOE Division of Scientific User Facilities
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We investigate the binding of single and quadruple hydrogen molecules on a positively charged Ca ion. By comparing with benchmark quantum Monte Carlo (QMC) calculations we demonstrate wide variability in other more approximate electronic-structure methods including common density functionals. Single determinant QMC calculations find no binding at short range by approximately 0.1 eV for the quadruple hydrogen molecule case, for a fixed hydrogen bond length of 0.77 angstrom. Density-functional calculations using common functionals such a local density approximation and B3LYP differ substantially from the QMC binding curve. We show that use of full Hartree-Fock exchange and Perdew-Burke-Ernzerhof (PBE) correlation (HFX + PBEC) obtains close agreement with the QMC results, both qualitatively and quantitatively. These results both motivate the use and development of improved functionals and indicate that caution is required applying electronic-structure methods to weakly bound systems such as hydrogen-storage materials based on metal-ion-decorated nanostructures.
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