The Journal of Chemical Physics 139, 084117 (2013)
Simulations of nanocrystals under pressure: Combining electronic enthalpy and linear-scaling density-functional theory
Niccolò R. C. Corsini1, Andrea Greco1, Nicholas D. M. Hine1,2, Carla Molteni3 and Peter D. Haynes1
1Department of Physics and Department of Materials, Imperial College London,
Exhibition Road, London SW7 2AZ, United Kingdom
2Cavendish Laboratory, J. J. Thomson Avenue,
Cambridge CB3 0HE, United Kingdom
3Department of Physics, King's College London,
Strand, London WC2R 2LS, United Kingdom
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.
Last updated: 2 September 2013