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Accurate ionic forces and geometry optimization in linear-scaling density-functional theory with local orbitals

Accurate ionic forces and geometry optimization in linear-scaling density-functional theory with local orbitals
Accurate ionic forces and geometry optimization in linear-scaling density-functional theory with local orbitals
Linear scaling methods for density-functional theory (DFT) simulations are formulated in terms of localized orbitals in real space, rather than the delocalized eigenstates of conventional approaches. In local-orbital methods, relative to conventional DFT, desirable properties can be lost to some extent, such as the translational invariance of the total energy of a system with respect to small displacements and the smoothness of the potential-energy surface. This has repercussions for calculating accurate ionic forces and geometries. In this work we present results from onetep, our linear scaling method based on localized orbitals in real space. The use of psinc functions for the underlying basis set and on-the-fly optimization of the localized orbitals results in smooth potential-energy surfaces that are consistent with ionic forces calculated using the Hellmann-Feynman theorem. This enables accurate geometry optimization to be performed. Results for surface reconstructions in silicon are presented, along with three example systems demonstrating the performance of a quasi-Newton geometry optimization algorithm: an organic zwitterion, a point defect in an ionic crystal, and a semiconductor nanostructure.

1550-235X
195102-[10 pages]
Hine, Nicholas
38da4176-484b-40fd-bb08-2948da585360
Robinson, Mark
0191ef40-12cc-4b4d-9bcd-5547087add95
Haynes, Peter
73c1a6e9-2814-4b3f-87a2-ca020786d943
Skylaris, Chris-Kriton
8f593d13-3ace-4558-ba08-04e48211af61
Payne, Mike
bb065804-2558-471b-ad21-afdfd4889f11
Mostofi, Arash
3552c94d-3757-43f3-9e82-7e55897eb56d
Hine, Nicholas
38da4176-484b-40fd-bb08-2948da585360
Robinson, Mark
0191ef40-12cc-4b4d-9bcd-5547087add95
Haynes, Peter
73c1a6e9-2814-4b3f-87a2-ca020786d943
Skylaris, Chris-Kriton
8f593d13-3ace-4558-ba08-04e48211af61
Payne, Mike
bb065804-2558-471b-ad21-afdfd4889f11
Mostofi, Arash
3552c94d-3757-43f3-9e82-7e55897eb56d

Hine, Nicholas, Robinson, Mark, Haynes, Peter, Skylaris, Chris-Kriton, Payne, Mike and Mostofi, Arash (2011) Accurate ionic forces and geometry optimization in linear-scaling density-functional theory with local orbitals. Physical Review B, 83 (19), 195102-[10 pages]. (doi:10.1103/PhysRevB.83.195102).

Record type: Article

Abstract

Linear scaling methods for density-functional theory (DFT) simulations are formulated in terms of localized orbitals in real space, rather than the delocalized eigenstates of conventional approaches. In local-orbital methods, relative to conventional DFT, desirable properties can be lost to some extent, such as the translational invariance of the total energy of a system with respect to small displacements and the smoothness of the potential-energy surface. This has repercussions for calculating accurate ionic forces and geometries. In this work we present results from onetep, our linear scaling method based on localized orbitals in real space. The use of psinc functions for the underlying basis set and on-the-fly optimization of the localized orbitals results in smooth potential-energy surfaces that are consistent with ionic forces calculated using the Hellmann-Feynman theorem. This enables accurate geometry optimization to be performed. Results for surface reconstructions in silicon are presented, along with three example systems demonstrating the performance of a quasi-Newton geometry optimization algorithm: an organic zwitterion, a point defect in an ionic crystal, and a semiconductor nanostructure.

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Published date: 2 May 2011
Organisations: Chemistry, Computational Systems Chemistry

Identifiers

Local EPrints ID: 336978
URI: http://eprints.soton.ac.uk/id/eprint/336978
ISSN: 1550-235X
PURE UUID: c3ca147d-4ba8-4d50-a876-7d409193af18
ORCID for Chris-Kriton Skylaris: ORCID iD orcid.org/0000-0003-0258-3433

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Date deposited: 12 Apr 2012 14:10
Last modified: 10 Dec 2019 01:43

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