English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

In ab initio calculations of electronic structures, total energies, andforces, it is convenient and often even necessary to employ a broadening of theoccupation numbers. If done carefully, this improves the accuracy of thecalculated electron densities and total energies and stabilizes the convergenceof the iterative approach towards self-consistency. However, such a boardeningmay lead to an error in the calculation of the forces. Accurate forces areneeded for an efficient geometry optimization of polyatomic systems and for abinitio molecular dynamics (MD) calculations. The relevance of this error andpossible ways to correct it will be discussed in this paper. The first approachis computationally very simple and in fact exact for small MD time steps. Thisis demonstrated for the example of the vibration of a carbon dimer and for therelaxation of the top layer of the (111)-surfaces of aluminium and platinum.The second, more general, scheme employs linear-response theory and is appliedto the calculation of the surface relaxation of Al(111). We will show that thequadratic dependence of the forces on the broadening width enables an efficientextrapolation to the correct result. Finally the results of these correctionmethods will be compared to the forces obtained by using the smearing scheme,which has been proposed by Methfessel and Paxton.

Errors in Hellmann-Feynman forces due to occupation-number broadening and how they can be corrected