Issue 19, 2017

Exploration of crystal structures and phase transitions in Hf3N4

Abstract

Using the adaptive genetic algorithm (AGA) crystal structure prediction method, we explored the stable/meta-stable phases of Hf3N4. A new ground-stage phase (C2/m) of Hf3N4 at ambient pressure was predicted. Calculated phonon dispersion and elastic constants of this phase showed it to be dynamically and mechanically stable. We also produced a pressure–temperature phase diagram of Hf3N4 that included the C2/m, orthorhombic Zr3N4-type (Pnam) and I[4 with combining macron]3d phases. Our results revealed that increasing the pressure and temperature would transform the C2/m phase of Hf3N4 to the I[4 with combining macron]3d and Pnam phases, respectively. Although the orthorhombic Zr3N4-type phase was indicated to be metastable over all pressures, the contributions from its larger vibrational entropies than for C2/m indicated it to be stable only between temperatures of ∼414 and ∼686 K at low pressure. The I[4 with combining macron]3d structure was calculated to be stable at a wide range of temperatures at high pressure and at a wide range of pressures at high temperature, with this result being in good agreement with the experimental results.

Graphical abstract: Exploration of crystal structures and phase transitions in Hf3N4

Article information

Article type
Paper
Submitted
18 Mar 2017
Accepted
10 Apr 2017
First published
10 Apr 2017

CrystEngComm, 2017,19, 2608-2613

Exploration of crystal structures and phase transitions in Hf3N4

F. Zheng, Y. Fang, S. Yu, S. Wu and Z. Zhu, CrystEngComm, 2017, 19, 2608 DOI: 10.1039/C7CE00524E

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