A Method of Nano-Sized Intermetallic Compounds and Heusler Phases Entropy Estimation

A new approach to predict the standard entropy of crystal intermetallic compounds and Heusler phases with fairy good accuracy was developed. In the conjunction with Jiang and Yang's equation which links the entropy of nano-sized materials with crystal ones, this approach allows to make estimations for nano- intermetallic materials and nano-Heusler phases. The approach is based on the Grimvall and coworkers' idea that the difference in the atomic masses accounts for almost all differences in the entropy among chemically similar compounds. This idea was implemented through the correlation equations between natural logarithm of the entropy of binary intermetallic compounds and the reduced mass of a pair of interacting atoms in the compound. The regularities that link together fitting constants of the correlation equations for different groups of similar compounds have been revealed. Based on the obtained correlations, simple and well-defined predictive schemes were developed. The constituent additivity method as an expression of the additivity principle for entropy has been successfully applied for the standard entropy prediction of complex (M m X n , n ≥ 2) intermetallic compounds and Heusler phases. The mean deviations of the standard entropy estimations from experimental and/or tabulated data with the use of the obtained correlations are in the range of ±1-5%. In the conjunction with the Debye theory of heat capacity, the proposed schemes provide the assessment of the temperature dependences of intermetallic compounds and Heusler phases entropy.