scholarly journals Towards the First-Principles Investigation of Ordering Dynamics

2005 ◽  
Vol 475-479 ◽  
pp. 3075-3080 ◽  
Author(s):  
Tetsuo Mohri ◽  
Munekazu Ohno ◽  
Ying Chen
Keyword(s):  
First Principles ◽  
Coarse Graining ◽  
Cluster Variation Method ◽  
Field Method ◽  
Energy Functional ◽  
First Principles Calculation ◽  
Phase Field Method ◽  
Variation Method ◽  
Gradient Energy ◽  
Cluster Variation

Phase Field Method (PFM) is hybridized with Cluster Variation Method (CVM) to investigate the ordering dynamics of L10-disorder transition at atomistic and microstructural scales simultaneously. For this, coarse graining operation is attempted on the inhomogeneous free energy functional of CVM. The resultant gradient energy coefficient is found out to be dependent on temperature and order parameters, which is in marked contrast to a conventional PFM formalism. Electronic structure total energy calculations for Fe-Pd system are incorporated to the hybridized scheme and the first principles calculation of microstructural evolution process is attempted.

Phase Field Calculations with CVM Free Energy within Square Approximation

2007 ◽  
Vol 561-565 ◽  
pp. 1935-1940
Author(s):  
Tetsuo Mohri ◽  
Nao Fujihashi ◽  
Ying Chen
Keyword(s):  
Free Energy ◽  
Phase Field ◽  
Stoichiometric Composition ◽  
Sharp Decrease ◽  
Cluster Variation Method ◽  
Field Method ◽  
Phase Field Method ◽  
Square Lattice ◽  
Variation Method ◽  
Cluster Variation

Phase Field Method is combined with the Cluster Variation Method within the square approximation, and the multiscale ordering behavior from atomistic to microstructural evolution process of ordered domains in the two dimensional square lattice is investigated. The transition temperature is determined at 1:1 stoichiometric composition and it is confirmed that the transition is of the second order. The growth process of the ordered domains is visualized and it is revealed that the sharp decrease of the free energy takes place during the process.

First Principles Calculation of Phase Stability of High Temperature Intermetallic Alloys

1990 ◽  
Vol 213 ◽  
Author(s):  
J. Mikalopas ◽  
P.A. Sterne ◽  
M. Sluiter ◽  
P.E.A. Turchi
Keyword(s):  
First Principles ◽  
Strong Dependence ◽  
Cluster Variation Method ◽  
First Principles Calculation ◽  
Variation Method ◽  
Many Body ◽  
Coherent Phase Diagram ◽  
Cluster Variation ◽  
The Many ◽  
Many Body Interactions

ABSTRACTOne way to calculate the coherent phase diagram of an alloy based on first principles methods is to compute the ground state total energy for various ordered configurations, from which many-body interactions can be calculated and employed in a thermodynamic model. If the Connolly and Williams method (CWM) is used to extract the many-body interactions from the calculated total energies, the resulting many-body interactions can exhibit a strong dependence on the choice of ordered configurations and multi-site clusters, and the accuracy and convergence of the CWM energy expansion is not assured. To overcome this difficulty, a successful systematic method for implementing the CWM is proposed. This approach is applied to a study of the fcc-based Ni-V and Pd-V substitutional alloys and these interaction parameters together with the cluster variation method (CVM) are used to calculate phase diagrams.

From Phase Equilibria to Transformation Dynamics

2007 ◽  
Vol 263 ◽  
pp. 21-30 ◽  
Author(s):  
Tetsuo Mohri ◽  
Munekazu Ohno ◽  
Ying Chen
Keyword(s):  
Phase Transformation ◽  
Phase Equilibria ◽  
First Principles ◽  
Materials Science ◽  
Present Report ◽  
Cluster Variation Method ◽  
First Principles Calculation ◽  
Phase Field Method ◽  
Variation Method ◽  
First Principles Calculations

First principles calculations have been applied in various fields in Materials Science. The authors have been attempting to reproduce a binary phase diagram by combining FLAPW electronic structure total energy calculations with Cluster Variation Method of statistical mechanics. Such a first principles calculation for static equilibrium has been quite successful for a series of Febased alloy systems. Recently, main attention is directed towards the extension of the first principles calculation to phase transformation dynamics by incorporating Phase Field Method. A series of preliminary calculations on disorder-L10 ordering in Fe-Pd and –Pt are satisfactory and the evolution process of Anti-Phase Boundaries was reproduced. In the present report, first-principles calculations of phase equilibria and phase transformation are briefly reviewed. Particular focuses are placed on coarse graining operation which authors developed and and time scaling as a remaining problem.

Multi-Scale Phase Field Simulation of Disorder-Order Transition, Combined with Cluster Variation and Path Probability Methods

2009 ◽  
Vol 631-632 ◽  
pp. 401-406
Author(s):  
Munekazu Ohno ◽  
Ying Chen ◽  
Tetsuo Mohri
Keyword(s):  
Phase Field ◽  
Cluster Variation Method ◽  
Field Method ◽  
Phase Field Method ◽  
Variation Method ◽  
Probability Method ◽  
Multi Scale ◽  
Probability Methods ◽  
Cluster Variation ◽  
Path Probability Method

Multi-scale simulation of ordering process from electronic, atomistic scales to microstructural scale was carried out by hybridizing Phase Field Method (PFM) and Cluster Variation Method (CVM). The hybrid model was applied to disorder-L10 ordering process in Fe-Pd system. Furthermore, computation of relaxation constants in the PFM was attempted based on Path Probability Method (PPM) which is the time evolution version of the CVM, within a linearized analysis of order-order relaxation process.

CVM-based first-principles calculations for Fe-based alloys

2011 ◽  
Vol 1296 ◽  
Author(s):  
Tetsuo Mohri
Keyword(s):  
Free Energy ◽  
First Principles ◽  
Cluster Variation Method ◽  
Phase Field Method ◽  
Variation Method ◽  
Probability Method ◽  
First Principles Calculations ◽  
Wide Range ◽  
Cluster Variation ◽  
Alloy Systems

ABSTRACTCluster Variation Method (CVM) has been recognized as one of the most reliable theoretical tools to incorporate wide range of atomic correlations into a free energy formula. By combining CVM with electronic structure total energy calculations, one can perform first-principles calculations of alloy phase equilibria. The author attempted such CVM-based first-principles calculations for various alloy systems including noble metal alloys, transition-noble alloys, III-V semiconductor alloys and Fe-based alloy systems. Furthermore, CVM can be extended to two kinds of kinetics calculations. One is Path Probability Method (PPM) which is the natural extension of the CVM to time domain and is quite powerful to investigate atomistic kinetic phenomena. The other one is Phase Field Method (PFM) with the CVM free energy as a homogeneous free energy density term in the PFM. The author’s group applied the latter procedure to study time evolution process of ordered domains associated with disorder-L10 transition in Fe-Pd and Fe-Pt systems. CVM has, therefore, a potential applicability for the systematic studies covering atomistic to microstructural scales. It has been, however, pointed out that the conventional CVM is not able to include local lattice relaxation effects and that the resulting order-disorder transition temperatures are overestimated. In order to circumvent such inconveniences, Continuous Displacement Cluster Variation Method (CDCVM) has been developed. Since first-principles CDCVM calculations are still beyond the scope at the present stage, preliminary results on the two dimensional square lattice and an fcc lattice with primitive Lennard-Jones type potentials are demonstrated in the last section.

First-principle Thoery of Phase Stability, Phase Equilibria and Phase Transition of Ordered Compounds

2006 ◽  
Vol 980 ◽  
Author(s):  
Tetsuo Mohri
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Future Prospect ◽  
Cluster Variation Method ◽  
First Principles Calculation ◽  
Variation Method ◽  
Cluster Variation ◽  
The Stability ◽  
Noble Metal Alloys ◽  
Alloy Systems

AbstractFirst-principles theory of alloys is based on electronic structure calculation at the ground state and statistical mechanics calculation at finite temperatures. The former clarifies the stability of an ordered compound against competing phases and the latter is employed mainly to derive a phase diagram. The author performed a series of first-principles investigations on binary alloy systems including noble metal alloys, semiconductor alloys and Fe-based alloy systems by combining FLAPW electronic structure total energy calculations with Cluster Variation Method. Recently, the theoretical framework is extended even to calculate microstructural evolution process. By exemplifying Fe-based alloy systems, the progress of the first-principles calculation is reviewed and future prospect is discussed.

A First Principles Examination of Phase Stability in Fcc-Based Ni-V Substitutional Alloys

1990 ◽  
Vol 186 ◽  
Author(s):  
J. Mikalopas ◽  
P.E.A. Turchi ◽  
M. Sluiter ◽  
P.A. Sterne
Keyword(s):  
Phase Stability ◽  
Ground State ◽  
First Principles ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Many Body ◽  
Cluster Variation ◽  
Many Body Interactions ◽  
Ground State Energies ◽  
Substitutional Alloys

AbstractThe phase stability of fcc-based Ni-V substitutional alloys is investigated using linear muffin-tin orbitals total energy (LMTO) calculations. The method of Connolly and Williams (CWM) is used to extract many body interactions from the ground state energies of selected ordered configurations. These interactions are used in conjunction with the cluster variation method (CVM) to calculate the alloy phase diagram. The dependence of the interactions on the choice of configurations used to calculate them is examined.

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