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DFT Predictions of Crystal Structure, Electronic Structure, Compressibility, and Elastic Properties of Hf–Al–C Carbides
Author(s) -
Bai Yuelei,
Duff Andrew,
Jayaseelan Daniel Doni,
Wang Rongguo,
He Xiaodong,
Lee William Edward
Publication year - 2016
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.14361
Subject(s) - ductility (earth science) , ternary operation , bulk modulus , materials science , density functional theory , max phases , compressibility , crystallography , carbide , elastic modulus , crystal structure , bond length , thermodynamics , chemistry , composite material , computational chemistry , physics , creep , computer science , programming language
To understand the potential for use of the Hf–Al–C ternary compounds, (HfC) n A l 3 C 2 (Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 ) and (HfC) n A l 4 C 3 (Hf 2 Al 4 C 5 and Hf 3 Al 4 C 6 ) were investigated using density functional theory, including crystal structure, electronic structure, compressibility, and elastic properties. The theoretical density of (HfC) n A l 3 C 2 (4.10–4.16 g/cm 3 ) is higher than that of (HfC) n A l 4 C 3 (3.92–3.98 g/cm 3 ), due to the smaller number of lighter Al–C layers. With increasing numbers of Hf–C layers, the Hf–C and Al–C bond lengths remain almost unchanged. In none of the compounds is there a gap around the Fermi energy ( E f ), which implies they are metal‐like conductors. With increasing pressure, there is greater shrinkage along the c axis than the a axis. The bond stiffness increases with increasing pressure. In general, (HfC) n A l 3 C 2 has higher elastic stiffness than (HfC) n A l 4 C 3 , with the moduli increasing with the number of Hf–C layers. The Hf–Al–C compounds as well as the brittle Zr–Al–C compounds all have low shear moduli/bulk moduli ratio ( G / B ) from 0.71 to 0.78, suggesting that the G / B ratio is not always a suitable measure of ductility.