Electron-density critical points analysis and catastrophe theory to forecast structure instability in periodic solids

Marcello Merli, Alessandro Pavese

Risultato della ricerca: Article

6 Citazioni (Scopus)

Abstract

The critical points analysis of electron density, i.e. ρ(x), from ab initio calculations is used in combination with the catastrophe theory to show a correlation between ρ(x) topology and the appearance of instability that may lead to transformations of crystal structures, as a function of pressure/temperature. In particular, this study focuses on the evolution of coalescing non-degenerate critical points, i.e. such that ρ(xc) = 0 and λ1, λ2, λ3≠ 0 [λ being the eigenvalues of the Hessian of ρ(x) at xc], towards degenerate critical points, i.e. ρ(xc) = 0 and at least one λ equal to zero. The catastrophe theory formalism provides a mathematical tool to model ρ(x) in the neighbourhood of xcand allows one to rationalize the occurrence of instability in terms of electron-density topology and Gibbs energy. The phase/state transitions that TiO2(rutile structure), MgO (periclase structure) and Al2O3(corundum structure) undergo because of pressure and/or temperature are here discussed. An agreement of 3-5% is observed between the theoretical model and experimental pressure/temperature of transformation.Electron-density topology is used to detect instability in periodic solids.
Lingua originaleEnglish
pagine (da-a)102-111
Numero di pagine10
RivistaACTA CRYSTALLOGRAPHICA. SECTION A, FOUNDATIONS AND ADVANCES
Volume74
Stato di pubblicazionePublished - 2018

All Science Journal Classification (ASJC) codes

  • Structural Biology
  • Biochemistry
  • Materials Science(all)
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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