Atomistic deformation modes and intrinsic brittleness of Al{sub 4}SiC{sub 4}: A first-principles investigation
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)
From crystallographic point of view, Al{sub 4}SiC{sub 4} can be described as Al{sub 4}C{sub 3}-type and hexagonal SiC-type structural units alternatively stacked along [0001] direction. However, relationship between this layered crystal structure and mechanical properties is not fully established for Al{sub 4}SiC{sub 4}, except for the reported bulk modulus locating between those of Al{sub 4}C{sub 3} and SiC. Based on the first-principles pseudopotential total energy method, we calculated the elastic stiffness of Al{sub 4}SiC{sub 4}, and reported on its ideal tensile and shear stress-strain relationships considering different structural deformation modes. Elastic properties of Al{sub 4}SiC{sub 4} are dominated by the Al{sub 4}C{sub 3}-type structural units and exhibit similar results with those of Al{sub 4}C{sub 3}. Furthermore, the atomistic deformation modes of Al{sub 4}SiC{sub 4} upon tensile and shear deformations are illustrated and compared with Al{sub 4}C{sub 3} as well. Since the tension-induced bond breaking occurs inside the constitutive Al{sub 4}C{sub 3}-type unit, the ternary carbide has similar ideal tensile strength with Al{sub 4}C{sub 3}. On the other hand, despite the softening of strong coupling between Al{sub 4}C{sub 3}- and SiC-type structural units is involved in shear, the shear strength for Al{sub 4}SiC{sub 4} is, however, lower than the tensile strength, since p-state involved Al-C bonds respond more readily to the shear deformation than to tension. In addition, based on the comparison of strain energies at the maximum stresses, i.e., ideal strengths, for both tension and shear, we suggest that structural failure occurs in tensile deformation firstly and, thus confirms an intrinsic brittleness of Al{sub 4}SiC{sub 4}. For crystal structure arranged in alternatively stacking configuration, such as Al{sub 4}SiC{sub 4}, mechanical properties can be traced back to the constituent units, and are also related to the coupling strengths between each constituent unit. The results might provide a computational method to predict ductile or brittle response of a solid to applied deformations.
- OSTI ID:
- 20853853
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 74, Issue 17; Other Information: DOI: 10.1103/PhysRevB.74.174112; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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