Peter Haynes

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We present a new method for performing fast Fourier transforms for electronic structure calculations on parallel computers which minimises the latency cost involved in communication between nodes. We compare the new and traditional methods in theory and in practice, and thus suggest the conditions under which the new method will be more efficient than(More)
We present a detailed comparison between ONETEP, our linear-scaling density functional method, and the conventional pseudopotential plane wave approach in order to demonstrate its high accuracy. Further comparison with all-electron calculations shows that only the largest available Gaussian basis sets can match the accuracy of routine ONETEP calculations.(More)
We present calculations of formation energies of defects in an ionic solid (Al(2)O(3)) extrapolated to the dilute limit, corresponding to a simulation cell of infinite size. The large-scale calculations required for this extrapolation are enabled by developments in the approach to parallel sparse matrix algebra operations, which are central to(More)
Contrary to previous simulation results on the existence of amorphous intergranular films at high-angle twist grain boundaries (GBs) in elemental solids such as silicon, recent experimental results imply structural order in some high-angle boundaries. With a novel protocol for simulating twist GBs, which allows the number of atoms at the boundary to vary,(More)
An overview of the ONETEP (Order-N Electronic Total Energy Package) code is presented, focusing on the twin aims of overall linear scaling and controlled accuracy. The method is outlined, including a description of the density-matrix formulation of density-functional theory, and the optimisation procedures for both the density-kernel and the local orbitals(More)
A detailed study of energy differences between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO gaps) in protein systems and water clusters is presented. Recent work questioning the applicability of Kohn-Sham density-functional theory to proteins and large water clusters (Rudberg 2012 J. Phys.: Condens. Matter 24 072202) has(More)
We present a method for calculating the kinetic energy of localised functions represented on a regular real space grid. This method uses fast Fourier transforms applied to restricted regions commensurate with the simulation cell and is applicable to grids of any symmetry. In the limit of large systems it scales linearly with system size. Comparison with the(More)
This paper provides a general overview of the methodology implemented in onetep (Order-N Electronic Total Energy Package), a parallel density-functional theory code for large-scale first-principles quantum-mechanical calculations. The distinctive features of onetep are linear-scaling in both computational effort and resources, obtained by making(More)
NMR chemical shifts for an L-alanine molecular crystal are calculated using ab initio plane wave density functional theory. Dynamical effects including anharmonicity may be included by averaging chemical shifts over an ensemble of structural configurations generated using molecular dynamics (MD). The time scales required mean that ab initio MD is(More)
We describe the algorithms we have developed for linear-scaling plane wave density functional calculations on parallel computers as implemented in the ONETEP program. We outline how ONETEP achieves plane wave accuracy with a computational cost which increases only linearly with the number of atoms by optimising directly the single-particle density matrix(More)