Journal
JOURNAL OF ADVANCED CERAMICS
Volume 11, Issue 2, Pages 273-282Publisher
TSINGHUA UNIV PRESS
DOI: 10.1007/s40145-021-0531-9
Keywords
MAX phase; first-principles; damage tolerance; heat capacity; thermal expansion
Categories
Funding
- National Natural Science Foundation of China [51972080, 51772077]
- Shenzhen Science and Technology Program [KQTD2016112814303055]
- science foundation of National Key Laboratory of Science and Technology on Advanced Composites in Special Environments
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In this study, the structure, chemical bonding, and mechanical and thermodynamic properties of Mo2Ga2C were investigated using first-principles calculations. Mo2Ga2C was found to have a unique structure and high damage tolerance.
Mo2Ga2C is a new MAX phase with a stacking Ga-bilayer as well as possible unusual properties. To understand this unique MAX phase structure and promote possible future applications, the structure, chemical bonding, and mechanical and thermodynamic properties of Mo2Ga2C were investigated by first-principles. Using the bond stiffness model, the strongest covalent bonding (1162 GPa) was formed between Mo and C atoms in Mo2Ga2C, while the weakest Ga-Ga (389 GPa) bonding was formed between two Ga-atomic layers, different from other typical MAX phases. The ratio of the bond stiffness of the weakest bond to the strongest bond (0.33) was lower than 1/2, indicating the high damage tolerance and fracture toughness of Mo2Ga2C, which was confirmed by indentation without any cracks. The high-temperature heat capacity and thermal expansion of Mo2Ga2C were calculated in the framework of quasi-harmonic approximation from 0 to 1300 K. Because of the metal-like electronic structure, the electronic excitation contribution became more significant with increasing temperature above 300 K.
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