Phonons at the Gamma point and the Raman spectrum of the hexagonal Ge2Sb2Te5 were computed within density functional perturbation theory. The three different stackings of the Ge/Sb planes proposed in the experimental literature were considered. The theoretical Raman spectrum is similar for the three stackings with a marginally better agreement with experiments for the structure proposed by Matsunaga et al (2004 Acta Crystallogr. B 60 685) which assumes a disorder in Ge/Sb site occupation. Although the large broadening of the experimental Raman peaks prevents discriminating among the different stackings, the assignment of the Raman peaks to specific phonons is possible because the main features of the spectrum are rather insensitive to the actual distribution of atoms in the Sb/Ge sublattices. On the basis of the energetics (including configurational entropy) two stackings seem plausible candidates for GST, but only the mixed stacking by Matsunaga et al reproduces the spread of Ge/Sb-Te bond lengths measured experimentally.

Sosso, G., Caravati, S., Gatti, C., Assoni, S., & Bernasconi, M. (2009). Vibrational properties of hexagonal Ge2Sb2Te5 from first principles. JOURNAL OF PHYSICS. CONDENSED MATTER, 21(24), 245401 [10.1088/0953-8984/21/24/245401].

Vibrational properties of hexagonal Ge2Sb2Te5 from first principles

BERNASCONI, MARCO
2009

Abstract

Phonons at the Gamma point and the Raman spectrum of the hexagonal Ge2Sb2Te5 were computed within density functional perturbation theory. The three different stackings of the Ge/Sb planes proposed in the experimental literature were considered. The theoretical Raman spectrum is similar for the three stackings with a marginally better agreement with experiments for the structure proposed by Matsunaga et al (2004 Acta Crystallogr. B 60 685) which assumes a disorder in Ge/Sb site occupation. Although the large broadening of the experimental Raman peaks prevents discriminating among the different stackings, the assignment of the Raman peaks to specific phonons is possible because the main features of the spectrum are rather insensitive to the actual distribution of atoms in the Sb/Ge sublattices. On the basis of the energetics (including configurational entropy) two stackings seem plausible candidates for GST, but only the mixed stacking by Matsunaga et al reproduces the spread of Ge/Sb-Te bond lengths measured experimentally.
Articolo in rivista - Articolo scientifico
Scientifica
Calcoli ab-initio, struttura elettronica, spettroscopia vibrazionale
English
245401
Sosso, G., Caravati, S., Gatti, C., Assoni, S., & Bernasconi, M. (2009). Vibrational properties of hexagonal Ge2Sb2Te5 from first principles. JOURNAL OF PHYSICS. CONDENSED MATTER, 21(24), 245401 [10.1088/0953-8984/21/24/245401].
Sosso, G; Caravati, S; Gatti, C; Assoni, S; Bernasconi, M
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10281/6148
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