Investigation into Structural Phase Transitions in Layered Titanium-Oxypnictides by a Computational Phonon Analysis

Kousuke Nakano; Kenta Hongo; Ryo Maezono

doi:10.1021/acs.inorgchem.7b01709

Investigation into Structural Phase Transitions in Layered Titanium-Oxypnictides by a Computational Phonon Analysis

Inorg Chem. 2017 Nov 20;56(22):13732-13740. doi: 10.1021/acs.inorgchem.7b01709. Epub 2017 Nov 2.

Authors

Kousuke Nakano¹, Kenta Hongo^{2

3

4}, Ryo Maezono¹

Affiliations

¹ School of Information Science, JAIST , Asahidai 1-1, Nomi, Ishikawa 923-1292, Japan.
² Research Center for Advanced Computing Infrastructure, JAIST , Asahidai 1-1, Nomi, Ishikawa 923-1292, Japan.
³ PRESTO, Japan Science and Technology Agency (JST) , Kawaguchi, Saitama 332-0012, Japan.
⁴ Center for Materials Research by Information Integration, Research and Services Division of Materials Data and Integrated System, National Institute for Materials Science , Tsukuba 305-0047, Japan.

PMID: 29094926
DOI: 10.1021/acs.inorgchem.7b01709

Abstract

We applied ab initio phonon analysis to layered titanium-oxypnictides, Na₂Ti₂Pn₂O (Pn = As and Sb), and found a clear contrast between the cases with lighter/heavier pnictogen in comparison with experiments. The result completely explains the experimental structure at low temperature, C2/m for Pn = As, within the conventional charge density wave, while there arise discrepancies when the pnictogen gets heavier. Our phonon calculation using the GGA-PBE functional predicts that a Cmce polymorph is more stable than the experimentally observed one (Cmcm) for Pn = Sb. On the basis of further quantitative analysis, we suggest the possibility that the GGA-PBE functional does not properly reproduce the electron correlation effects for Pn = Sb, and this could be the reason for the present discrepancy.