Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 62: Methods in Computational Materials Modelling IV: Method development

MM 62.2: Vortrag

Donnerstag, 10. März 2016, 16:00–16:15, H53

Advanced Brillouin zone sampling for first-principles calculations — •Philip Hasnip and Matthew Probert — University of York, York, UK

In quantum mechanical materials models such as density functional theory (DFT), the material's wavefunction is expressed as a Bloch function multiplied by a phase factor exp{ik.r}, where k is drawn from the material's first Brillouin zone. Solutions to the quantum equations exist for all k and many quantities, including the total energy, require an integration over all k; these integrals are performed numerically on a finite mesh of sampling `k-points'.

The sampling density required for accurate integration cannot be known a priori, and varies from material to material; metallic states require particularly high k-point densities in order to reproduce the Fermi surface accurately, yet metallicity is an emergent property of the simulation and cannot be known reliably beforehand.

In this work we discuss the common methods for performing this k-point integration, highlighting the problems encountered in real simulations, and present alternative methods which ameliorate these difficulties. In particular we present a fast estimate for the k-point sampling error which may be used dynamically to guide simulations. The method will be illustrated with results using the Castep DFT program.