The configurational entropy of mixing of interstitials solid solutions

2010 ◽  
Vol 96 (16) ◽  
pp. 161904 ◽  
Author(s):  
Jorge Garcés
Keyword(s):  
Solid Solutions ◽  
Configurational Entropy ◽  
Entropy Of Mixing

scholarly journals Theoretical study of the phase transitions and electronic structure of (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N

2020 ◽  
Vol 56 (1) ◽  
pp. 305-312
Author(s):  
M. A. Gharavi ◽  
R. Armiento ◽  
B. Alling ◽  
P. Eklund
Keyword(s):  
Electronic Structure ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Solid Solutions ◽  
Rock Salt ◽  
Density Functional ◽  
Configurational Entropy ◽  
Mean Field Approximation ◽  
Random Structure ◽  
High Seebeck Coefficient

Abstract Rock-salt scandium nitride has gained interest due to its thermoelectric properties including a relatively high Seebeck coefficient. This motivates research for other semiconductor materials that exhibit similar electronic structure features as ScN. Using density functional theory calculations, we have studied disordered solid solutions of (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N using the special quasi-random structure model. The results show that within a mean-field approximation for the configurational entropy, the order–disorder phase transformation between the monoclinic LiUN2 prototype structure and the rock-salt cubic random alloy of these mentioned solid solutions occur at 740 K and 1005 K for (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N, respectively. The density-of-states for the two ternary compounds is also calculated and predicts semiconducting behavior with band gaps of 0.75 eV for (Zr0.5, Mg0.5)N and 0.92 eV for (Hf0.5, Mg0.5)N. The thermoelectric properties of both compounds are also predicted. We find that in the range of a moderate change in the Fermi level, a high Seebeck coefficient value at room temperature can be achieved.

scholarly journals Temperature-Dependent Configurational Entropy Calculations for Refractory High-Entropy Alloys

2021 ◽  
Author(s):  
Chiraag M Nataraj ◽  
Axel van de Walle ◽  
Amit Samanta
Keyword(s):  
Cluster Expansion ◽  
Configurational Entropy ◽  
Temperature Limit ◽  
Design Guidelines ◽  
Alloy Design ◽  
Solid Solution Alloy ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Entropy Of Mixing ◽  
The Ideal

AbstractThe cluster expansion formalism for alloys is used to construct surrogate models for three refractory high-entropy alloys (NbTiVZr, HfNbTaTiZr, and AlHfNbTaTiZr). These cluster expansion models are then used along with Monte Carlo methods and thermodynamic integration to calculate the configurational entropy of these refractory high-entropy alloys as a function of temperature. Many solid solution alloy design guidelines are based on the ideal entropy of mixing, which increases monotonically with $$N$$ N , the number of elements in the alloy. However, our results show that at low temperatures, the configurational entropy of these materials is largely independent of $$N$$ N , and the assumption described above only holds in the high-temperature limit. This suggests that alloy design guidelines based on the ideal entropy of mixing require further examination.

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