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

The lattice vibrations (phonon modes) of crystals underpin a large number ofmaterial properties. The harmonic phonon spectrum of a solid is the simplestdescription of its structural dynamics and can be straightforwardly derivedfrom the Hellman-Feynman forces obtained in a ground-state electronic structurecalculation. The presence of imaginary harmonic modes in the spectrum indicatesthat a structure is a local maximum on the athermal structural potential-energysurface and can yield important insight into the fundamental nature andphysical properties of a material. In this review article, we discuss thephysical significance of imaginary harmonic modes and distinguish between caseswhere imaginary modes are indicative of such phenomena, and those where theyreflect technical problems in the calculations. We outline basic approaches forexploring and renormalising imaginary modes, and demonstrate their utilitythrough a set of three case studies in the materials sciences.

The Physical Significance of Imaginary Phonon Modes in Crystals