Morgan, Dane and van de Walle, Axel and Ceder, Gerbrand and Althoff, Jeffrey D. and de-Fontaine, Didier (2000) Vibrational thermodynamics: coupling of chemical order and size effects. Modelling and Simulation in Materials Science and Engineering, 8 (3). pp. 295-309. ISSN 0965-0393 http://resolver.caltech.edu/CaltechAUTHORS:20111130-085807209
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The effects of chemical order on the vibrational entropy have been studied using first-principles and semi-empirical potential methods. Pseudopotential calculations on the Pd_3V system show that the vibrational entropy decreases by 0.07k_B upon disordering in the high-temperature limit. The decrease in entropy contradicts what would be expected from simple bonding arguments, but can be explained by the influence of size effects on the vibrations. In addition, the embedded-atom method is used to study the effects of local environments on the entropic contributions of individual Ni and Al atoms in Ni_3Al. It is found that increasing numbers of Al nearest neighbours decreases the vibrational entropy of an atom when relaxations are not included. When the system is relaxed, this effect disappears, and the local entropy is approximately uniform with increasing number of Al neighbours. These results are explained in terms of the large size mismatch between Ni and Al. In addition, a local cluster expansion is used to show how the relaxations increase the importance of long-range and multisite interactions.
|Additional Information:||© 2000 IOP Publishing Ltd. Received 16 September 1999, accepted for publication 1 March 2000. This work was supported by the Department of Energy, Office of Basic Energy Sciences under Contract Nos DE-FG02-96ER45571, DE-AC03-76SF00098 and DE-AC04-94AL85000. This work was also supported by NSF cooperative agreement ACI-9619020 through computing resources provided by the National Partnership for Advanced Computational Infrastructure (NPACI) at the San Diego Supercomputing Centre. Axel van de Walle acknowledges support from a ‘1967’ scholarship from the Natural Sciences and Engineering Research Council of Canada. The authors wish to thank G Garbulsky and S M Foiles for providing computer programs which made this work possible. The authors would also like to thank M D Asta for stimulating discussions.|
|Classification Code:||PACS: 65.40.G-; 62.20.D-; 63.50.-x|
|Official Citation:||Vibrational thermodynamics: coupling of chemical order and size effects Dane Morgan et al 2000 Modelling Simul. Mater. Sci. Eng. 8 295|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||19 Jan 2012 21:55|
|Last Modified:||26 Dec 2012 14:33|
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