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Towards efficient sampling of symmetric crystal structures: Operating in the asymmetric unit
Linköping University, Department of Physics, Chemistry and Biology.
2026 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This thesis explores the use of the asymmetric unit (ASU) as an efficient representation of symmetric crystal structures and it’s computational benefits for energy landscape sampling restricted to the degrees of freedom of Wyckoff positions and energy evaluation. Two methods for this representation are presented. The first is an ASU-based sampling approach in which only the degrees of freedom corresponding to unique configurations in the ASU are explored. It is shown that the resulting reduced energy landscapes can be expanded through symmetry operations to recover the complete landscapes without loss of information while providing a notable speed up. The second method introduces an energy evaluation scheme operating directly on the ASU by utilizing the equivalence of atoms belonging to the same Wyckoff orbit, enabling the energy of the full crystal structure to be expressed as a weighted sum over only the atoms in the ASU. The scheme can be integrated with a simple Lennard-Jones or machine-learned interatomic potential, significantly reducing the computational cost. The proposed methods are validated against conventional full unit cell calculations and are shown to reproduce the same results up to floating-point precision. The results demonstrate that operating directly in the ASU provides an accurate and computationally efficient approach for working with crystal structures.

Place, publisher, year, edition, pages
2026. , p. 34
Keywords [en]
Symmetric crystal structures, Asymmetric unit, Energy landscapes
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:liu:diva-225716ISRN: LITH-IFM-A-EX--26/4893--SEOAI: oai:DiVA.org:liu-225716DiVA, id: diva2:2079827
Subject / course
Technical Physics
Supervisors
Examiners
Available from: 2026-08-03 Created: 2026-06-25 Last updated: 2026-08-03Bibliographically approved

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Condensed Matter Physics

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CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
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  • asciidoc
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