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ɛ‐TiO, a Novel Stable Polymorph of Titanium Monoxide
Author(s) -
Amano Shinsaku,
Bogdanovski Dimitri,
Yamane Hisanori,
Terauchi Masami,
Dronskowski Richard
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201510479
Subject(s) - crystallography , monoxide , titanium , crystal structure , trigonal prismatic molecular geometry , phase (matter) , materials science , hexagonal phase , bismuth , hexagonal crystal system , chemistry , inorganic chemistry , octahedron , metallurgy , organic chemistry
For the Ti/O system, three titanium monoxide (TiO) phases (α, β, and γ) with defective NaCl‐type structures and a high‐temperature hexagonal phase (H) have been known for decades. In this work, single crystals of a novel polymorph, ɛ‐TiO, were synthesized by using a bismuth flux. X‐ray diffraction (XRD) revealed a hexagonal crystal structure ( a =4.9936(3) Å, c =2.8773(2) Å, P 6 ‾ 2 m ) that is isotypic with ɛ‐TaN. While the Ti atoms are surrounded by trigonal prismatic (sixfold coordination) and trigonal planar (threefold coordination) arrangements of O atoms, the O atoms are found in a pseudo‐square‐pyramidal arrangement of Ti atoms. First‐principles calculations of the formation enthalpy and the electron and phonon density of states and crystal orbital Hamilton population (COHP) analysis revealed that ɛ‐TiO is more stable than α‐TiO, which had previously been regarded as the most stable phase at low temperatures.