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Title: Towards a systematic assessment of errors in diffusion Monte Carlo calculations of semiconductors: Case study of zinc selenide and zinc oxide

The fixed node diffusion Monte Carlo (DMC) method has attracted interest in recent years as a way to calculate properties of solid materials with high accuracy. However, the framework for the calculation of properties such as total energies, atomization energies, and excited state energies is not yet fully established. Several outstanding questions remain as to the effect of pseudopotentials, the magnitude of the fixed node error, and the size of supercell finite size effects. Here, we consider in detail the semiconductors ZnSe and ZnO and carry out systematic studies to assess the magnitude of the energy differences arising from controlled and uncontrolled approximations in DMC. The former include time step errors and supercell finite size effects for ground and optically excited states, and the latter include pseudopotentials, the pseudopotential localization approximation, and the fixed node approximation. We find that for these compounds, the errors can be controlled to good precision using modern computational resources and that quantum Monte Carlo calculations using Dirac-Fock pseudopotentials can offer good estimates of both cohesive energy and the gap of these systems. We do however observe differences in calculated optical gaps that arise when different pseudopotentials are used.
Authors:
 [1] ;  [2] ;  [1] ;  [3]
  1. Department of Mechanical Science and Engineering, 1206 W Green Street, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)
  2. Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)
  3. (Japan)
Publication Date:
OSTI Identifier:
22493329
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 22; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACCURACY; ATOMIZATION; DIFFUSION; ERRORS; EXCITED STATES; MONTE CARLO METHOD; POTENTIALS; SEMICONDUCTOR MATERIALS; SOLIDS; ZINC; ZINC OXIDES; ZINC SELENIDES