### Session L28: Focus Session: Computational Materials Design - Property Optimization

2:30 PM–5:30 PM, Tuesday, March 22, 2011
Room: C156

Sponsoring Units: DCOMP DMP
Chair: Stefano Curtarolo, Duke University

Abstract ID: BAPS.2011.MAR.L28.6

### Abstract: L28.00006 : Possible calcium centers for hydrogen storage applications: An accurate many-body study by AFQMC calculations with large basis sets

3:54 PM–4:06 PM

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#### Authors:

Wirawan Purwanto
(College of William and Mary)

Henry Krakauer
(College of William and Mary)

Shiwei Zhang
(College of William and Mary)

Yudistira Virgus
(College of William and Mary)

Weak H$_2$ physisorption energies present a significant challenge to first-principle theoretical modeling and prediction of materials for H storage. There has been controversy regarding the accuracy of DFT on systems involving Ca cations. We use the auxiliary-field quantum Monte Carlo (AFQMC) method\footnote{ S.~Zhang and H.~Krakauer, Phys.~Rev.~Lett.~\textbf{90}, 136401 (2003); W.~A.~Al-Saidi, S.~Zhang and H.~Krakauer, J.~Chem.~Phys.~\textbf{124}, 224101 (2006). } to accurately predict the binding energy of Ca$^+$\,-\,4{H}$_2$. AFQMC scales as $N_{\textrm{\small{basis}}}^3$ and has demonstrated accuracy similar to or better than the gold-standard coupled cluster CCSD(T) method. We apply a modified Cholesky decomposition to achieve efficient Hubbard-Stratonovich transformation in AFQMC at large basis sizes. We employ the largest correlation consistent basis sets available, up to Ca/cc-pCV5Z, to extrapolate to the complete basis limit. The calculated potential energy curve exhibits binding with a double-well structure.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.L28.6