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Title: Simulations of nanocrystals under pressure: Combining electronic enthalpy and linear-scaling density-functional theory

We present an implementation in a linear-scaling density-functional theory code of an electronic enthalpy method, which has been found to be natural and efficient for the ab initio calculation of finite systems under hydrostatic pressure. Based on a definition of the system volume as that enclosed within an electronic density isosurface [M. Cococcioni, F. Mauri, G. Ceder, and N. Marzari, Phys. Rev. Lett.94, 145501 (2005)], it supports both geometry optimizations and molecular dynamics simulations. We introduce an approach for calibrating the parameters defining the volume in the context of geometry optimizations and discuss their significance. Results in good agreement with simulations using explicit solvents are obtained, validating our approach. Size-dependent pressure-induced structural transformations and variations in the energy gap of hydrogenated silicon nanocrystals are investigated, including one comparable in size to recent experiments. A detailed analysis of the polyamorphic transformations reveals three types of amorphous structures and their persistence on depressurization is assessed.
Authors:
; ;  [1] ;  [1] ;  [2] ;  [3]
  1. Department of Physics and Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)
  2. (United Kingdom)
  3. Department of Physics, King's College London, Strand, London WC2R 2LS (United Kingdom)
Publication Date:
OSTI Identifier:
22303584
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 139; Journal Issue: 8; Other Information: (c) 2013 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 77 NANOSCIENCE AND NANOTECHNOLOGY; 97 MATHEMATICAL METHODS AND COMPUTING; DENSITY FUNCTIONAL METHOD; DEPRESSURIZATION; ENERGY GAP; ENTHALPY; MOLECULAR DYNAMICS METHOD; NANOSTRUCTURES; OPTIMIZATION; SIMULATION; SOLVENTS