Monolayers of atomic or molecular adsorbates, weakly adsorbed on ionic solids such as NaCl or MgO, are benchmark systems for testing the accuracy of electronic structure methods designed for periodic systems.  These electronic structure methods are typically assessed by comparing the predicted properties of monolayers with experimental observations.  However, real-world adsorbed monolayers undergo quantum mechanical zero-point motion; when this zero-point motion is substantial, then zero-point corrections must be applied when theoretical predictions are compared with experimental observations.  Here we present quantum Monte Carlo calculations of the zero-point energies of Ar monolayers on MgO(100) surfaces.  Recent studies [Usvyat et al., Phys. Rev. B 86 , 045412 (2012)] suggest that in this system, the zero-point energy of the Ar monolayer must be computed to an accuracy of better than 0.05 kcal/mol, or substantially beyond 'chemical accuracy', to allow theoretical results to be compared with experiment.  We describe modifications of our QSATS code [Hinde, Comput. Phys. Commun. 182 , 2339 (2011)] that enable these high-accuracy calculations, and investigate the importance of dipole-dipole interactions in the Ar monolayer from localized Ar dipoles induced by the near-surface electric field of the MgO(100) substrate.

Accurate zero-point energies for Ar monolayers adsorbed on MgO(100)

247th National Meeting (2014)

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