scholarly journals Configurational Entropy in Multicomponent Alloys: Matrix Formulation from Ab Initio Based Hamiltonian and Application to the FCC Cr-Fe-Mn-Ni System

Entropy ◽  
2019 ◽  
Vol 21 (1) ◽  
pp. 68 ◽  
Author(s):  
Antonio Fernández-Caballero ◽  
Mark Fedorov ◽  
Jan Wróbel ◽  
Paul Mummery ◽  
Duc Nguyen-Manh
Keyword(s):  
Solid Solution ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Ab Initio ◽  
Density Functional ◽  
Elevated Temperatures ◽  
Thermodynamic Integration ◽  
Matrix Formulation ◽  
Configuration Entropy ◽  
Multi Body

Configuration entropy is believed to stabilize disordered solid solution phases in multicomponent systems at elevated temperatures over intermetallic compounds by lowering the Gibbs free energy. Traditionally, the increment of configuration entropy with temperature was computed by time-consuming thermodynamic integration methods. In this work, a new formalism based on a hybrid combination of the Cluster Expansion (CE) Hamiltonian and Monte Carlo simulations is developed to predict the configuration entropy as a function of temperature from multi-body cluster probability in a multi-component system with arbitrary average composition. The multi-body probabilities are worked out by explicit inversion and direct product of a matrix formulation within orthonomal sets of point functions in the clusters obtained from symmetry independent correlation functions. The matrix quantities are determined from semi canonical Monte Carlo simulations with Effective Cluster Interactions (ECIs) derived from Density Functional Theory (DFT) calculations. The formalism is applied to analyze the 4-body cluster probabilities for the quaternary system Cr-Fe-Mn-Ni as a function of temperature and alloy concentration. It is shown that, for two specific compositions (Cr 25Fe 25Mn 25Ni 25 and Cr 18Fe 27Mn 27Ni 28), the high value of probabilities for Cr-Fe-Fe-Fe and Mn-Mn-Ni-Ni are strongly correlated with the presence of the ordered phases L1 2 -CrFe 3 and L1 0-MnNi, respectively. These results are in an excellent agreement with predictions of these ground state structures by ab initio calculations. The general formalism is used to investigate the configuration entropy as a function of temperature and for 285 different alloy compositions. It is found that our matrix formulation of cluster probabilities provides an efficient tool to compute configuration entropy in multi-component alloys in a comparison with the result obtained by the thermodynamic integration method. At high temperatures, it is shown that many-body cluster correlations still play an important role in understanding the configuration entropy before reaching the solid solution limit of high-entroy alloys (HEAs).

Magnetic Phase Diagram of Transition Metal Doped ZnO from Density Functional Theory Calculations and Monte Carlo Simulations

2010 ◽  
Vol 1260 ◽  
Author(s):  
Sanjeev K. Nayak ◽  
Heike C. Herper ◽  
Peter Entel
Keyword(s):  
Monte Carlo ◽  
Curie Temperature ◽  
Monte Carlo Simulations ◽  
Ab Initio ◽  
Density Functional ◽  
Magnetic Phase Diagram ◽  
Density Functional Theory Calculations ◽  
Antiferromagnetic Coupling ◽  
Doped Zno ◽  
Co Concentrations

AbstractTransition metals doped ZnO are possible candidates for multiferroics. Here, we have investigated the evolution of ferromagnetism due to Co dopants. The magnetic properties have been studied for Co concentrations from 0 to 100% by using ab-initio methods, i.e., KKR Green's function techniques. In order to estimate the Curie temperature we have performed Monte Carlo simulations with ab-initio calculated exchange parameters.From our calculations the onset of ferromagnetism occurs between 5 to 20% of Co depending on the numerical details of KKR method used. For Co concentrations larger than 50% the system is dominated by antiferromagnetic coupling and no Curie temperature can be obtained.

Thermodynamic Properties of Actinide Oxide Solid Solutions

2008 ◽  
Vol 1125 ◽  
Author(s):  
Lindsay C. Shuller ◽  
Niravun Pavenayotin ◽  
Rodney C. Ewing ◽  
Udo Becker
Keyword(s):  
Solid Solution ◽  
Monte Carlo ◽  
Ab Initio ◽  
Density Functional ◽  
Configurational Entropy ◽  
Enthalpy Of Mixing ◽  
Fluorite Structure ◽  
Excess Gibbs Free Energy ◽  
Cation Ordering ◽  
End Members

ABSTRACTDensity functional theory and Monte(Carlo methods were used to investigate the solid( solution behavior of actinide dioxides (AcO2). The end(members of interest include: ZrO2, ThO2, UO2, NpO2, and PuO2; all have the isometric fluorite structure. Ab initio and subsequent Monte( Carlo simulations are used to calculate the excess enthalpy of mixing (ΔHexcess), excess Gibbs free energy of mixing (ΔGexcess), and excess configurational entropy (ΔSexcess) for the above solid(solution series. From ΔGexcess, phase diagrams are derived and miscibility gaps identified. All of the binaries of the aforementioned end(members were studied; however, this paper focuses on the U1(xZrxO2 and Np1(xUxO2 binaries. About 25 at.% Zr can be in solid solution with the UO2 matrix above 1500 K, while Np is completely miscible in the UO2 matrix. Partial cation ordering was observed at all temperatures for the U1(xZrxO2 binary. The Np1(xUxO2 binary approaches perfect cation disorder at high temperatures (2000 K). The cation ordering scheme is not identified in this study because the number of cation(cation interaction parameters was limited by the single unit cell from the ab initio calculations.

Low-linear energy transfer radiolysis of liquid water at elevated temperatures up to 350°C: Monte-Carlo simulations

2011 ◽  
Vol 508 (4-6) ◽  
pp. 224-230 ◽  
Author(s):  
S. Sanguanmith ◽  
Y. Muroya ◽  
J. Meesungnoen ◽  
M. Lin ◽  
Y. Katsumura ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Energy Transfer ◽  
Monte Carlo Simulations ◽  
Liquid Water ◽  
Linear Energy Transfer ◽  
Elevated Temperatures

Constructing accurate interaction potentials to describe the microsolvation of protonated methane by helium atoms

2017 ◽  
Vol 19 (12) ◽  
pp. 8307-8321 ◽  
Author(s):  
Dennis Kuchenbecker ◽  
Felix Uhl ◽  
Harald Forbert ◽  
Georg Jansen ◽  
Dominik Marx
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Ab Initio ◽  
Path Integral ◽  
Interaction Potential ◽  
Stationary Point ◽  
Path Integral Monte Carlo ◽  
Interaction Potentials ◽  
Helium Atoms

An ab initio-derived interaction potential is derived and used in path integral Monte Carlo simulations to investigate stationary-point structures of CH5+ microsolvated by up to four helium atoms.

Demixing and ordering in Ni(Ti,Zr)(Sb,Sn) half-Heusler materials

2017 ◽  
Vol 19 (45) ◽  
pp. 30695-30702 ◽  
Author(s):  
Joaquin Miranda Mena ◽  
Thomas Gruhn
Keyword(s):  
Density Functional Theory ◽  
Monte Carlo ◽  
Phase Separation ◽  
Monte Carlo Simulations ◽  
Density Functional ◽  
Field Model ◽  
Mean Field ◽  
Study Phase ◽  
Mean Field Model ◽  
Functional Theory

We employed density functional theory, Monte Carlo simulations and a mean field model to study phase separation in thermoelectric Ni(Ti,Zr)(Sb,Sn) half-Heusler materials, simultaneously alloyed in the (Ti,Zr)- and (Sb,Sn) sublattices.

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