Crystal structures and mechanical properties of osmium diboride at high pressure

• Published in: Scientific reports Vol. 11; no. 1; p. 5754
• Main Authors: Wang, Yi X., Liu, Ying Y., Yan, Zheng X., Liu, Wei, Zhou, Gao L., Xiong, Ke Z.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11-03-2021; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/1034/1038; 639/766/119/2795; Approximation method; High pressure; Humanities and Social Sciences; Mechanical properties; multidisciplinary; Osmium; Pressure; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-85334-y

We have investigated the crystal structures and mechanical properties of osmium diboride (OsB
2
) based on the density functional theory. The structures of OsB
2
from 0 to 400 GPa were predicted using the particle swarm optimization algorithm structure prediction technique. The orthorhombic
Pmmn
structure of OsB
2
(
oP
6-OsB
2
) was found to be the most stable phase under zero pressure and it will transfer to the hexagonal
P
6
3
/
mmc
structure (
hP
6-OsB
2
) around 12.4 GPa. Meanwhile, we have discovered a new stable orthorhombic
Immm
structure (
oI
12-OsB
2
) above 379.6 GPa. After that, a thorough and comprehensive investigation on mechanical properties of different OsB
2
phases is performed in this work. Further studies showed that the hardness of
oP
6-OsB
2
and
hP
6-OsB
2
at zero pressure is 15.6 and 20.1 GPa, while that for
oI
12-OsB
2
under 400 GPa is 15.4 GPa, indicating that these three phases should be potentially hard materials rather than superhard materials. Finally, the pressure–temperature phase diagram of OsB
2
is constructed for the first time by using the quasi-harmonic approximation method. Our results showed that the transition pressures of
oP
6-OsB
2
 → 
hP
6-OsB
2
and
hP
6-OsB
2
 → 
oI
12-OsB
2
all decreases appreciably with the increase of temperature.