%0 Journal Article
%A Sánchez Torralba, Antonio
%A Bowler, David 
%A Miyazaki, Tsuyoshi
%A Gillan, Michael
%T Non-self-consistent density-functional theory exchange-correlation forces for GGA functionals
%D 2009
%@ 1549-9618
%U https://hdl.handle.net/20.500.14352/117196
%X When using density functional theory (DFT), generalized gradient approximation (GGA) functionals are often necessary for accurate modeling of important properties of biomolecules, including hydrogen-bond strengths and relative energies of conformers. We consider the calculations of forces using non-self-consistent (NSC) methods based on the Harris−Foulkes expression for energy. We derive an expression for the GGA NSC force on atoms, valid for a hierarchy of methods based on local orbitals, and discuss its implementation in the linear scaling DFT code Conquest, using a standard (White−Bird) approach. We investigate the use of NSC structural relaxations before full self-consistent relaxations as a method for improving convergence. Example calculations for glycine and small alanine peptides suggest that NSC pre-relaxations of the structure are indeed useful to save computer effort and time.
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