1Physical & Theoretical Chemistry Laboratory, South Parks Road, University of Oxford, Oxford OX1 3QZ, UK
2Theory of Condensed Matter group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Ave, Cambridge CB3 0HE, UK
3Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge MA, USA
We describe the algorithms we have developed for linear-scaling plane wave density functional calcula-tions 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 expressed in a psinc basis set. We describe in detail the novel algorithms we have developed for computing with the psinc basis set the quantities needed in the evaluation and optimisation of the total energy within our approach. For our parallel computations we use the general Message Passing Interface (MPI) library of subroutines to exchange data between proces-sors. Accordingly, we have developed efficient schemes for distributing data and computational load to processors in a balanced manner. We describe these schemes in detail and in relation to our algorithms for computations with a psinc basis. Results of tests on different materials show that ONETEP is an efficient parallel code that should be able to take advantage of a wide range of parallel computer architectures.