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Abstract:
The phonon spectra, phonon optical activities, thermal expansion and thermodynamic properties of ordered quaternary carbides M2TiAlC2 (M = Cr, Mo, W) and their ternary counterparts Ti(3)AIC(2) and Cr(3)AIC(2) are studied by first-principles phonon calculations. Phonon eigenvectors of all Raman and infrared modes are analyzed. We find that vibrational frequencies of some Raman active modes (A(1g) and E-2g) can be correlated to the strength and reduced mass of covalent M (4f)-C or metallic M (4f)-Al bond in all studied structures. Phonon mode-Gruneisen parameter and macroscopic Gruneisen constants are evaluated from phonon spectra. The thermal expansion coefficients, specific heats and isothermal bulk moduli at finite temperatures are obtained under the quasiharmonic approximation (QHA). The average linear thermal expansion coefficient (LTEC) values are found to be alpha(L) = 11.30 x 10(-6)K(-1), 7.15 x 10(-6)K(-1), 8.67 x 10(-6)K(-1), 10.29 x 10(-6)K(-1) and 15.70 x 10(-6)K(-1) for Cr(2)TiAIC(2), Mo(2)TiAIC(2), W(2)Ti(2)AIC(2), Ti(3)AIC(2) and Cr(3)AIC(2) in a range from 300 K to 1400 K, respectively. The hypothetical Cr(3)AIC(2) phase shows strong anharmonic effects in the calculated thermal expansion profile above 600 K. Using Slack-model, the thermal conductivities are also evaluated, and the values are kappa = 36.1 W/m K (34.4 W/m K, 27.2 W/m K) for Cr(2)TiAIC(2) (Mo(2)TiAIC(2), W(2)Ti(2)AIC(2)) at room temperature. (C) 2017 Elsevier B.V. All rights reserved.
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COMPUTATIONAL MATERIALS SCIENCE
ISSN: 0927-0256
Year: 2017
Volume: 134
Page: 67-83
2 . 5 3
JCR@2017
3 . 3 0 0
JCR@2020
ESI Discipline: MATERIALS SCIENCE;
ESI HC Threshold:217
JCR Journal Grade:2
CAS Journal Grade:3
Cited Count:
WoS CC Cited Count: 5
SCOPUS Cited Count: 6
ESI Highly Cited Papers on the List: 0 Unfold All
WanFang Cited Count:
Chinese Cited Count:
30 Days PV: 3