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

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Niccolo R. C. Corsini, Andrea Greco, Nicholas D. M. Hine, Carla Molteni, Peter D. Haynes

Original languageEnglish
Article number084117
Number of pages10
JournalJournal of Chemical Physics
Volume139
Issue number8
Early online date30 Aug 2013
DOIs
Accepted/In press29 Jul 2013
E-pub ahead of print30 Aug 2013

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Abstract

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. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

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