THERMODYNAMICS OF MATERIALS: FROM AB INITIO TO PHENOMENOLOGY
Abstract
Quantum mechanicalbased (or ab initio) methods are used to predict the stability properties of materials although their application is limited to relatively simple systems in terms of structures and number of alloy components. However thermodynamics of complex multicomponent alloys requires a more versatile approach afforded within the CALPHAD formalism. Despite its success, the lack of experimental data very often prevents the design of robust thermodynamic databases. After a brief survey of ab initio methodologies and CALPHAD, it will be shown how ab initio electronic structure methods can supplement in two ways CALPHAD for subsequent applications. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The other way, more involved, is the assessment of ab initio thermodynamics '{acute a} la CALPHAD'. It will be shown how these results can be used within CALPHAD to predict the equilibrium properties of multicomponent alloys. Finally, comments will be made on challenges and future prospects.
 Authors:
 Publication Date:
 Research Org.:
 Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 15014609
 Report Number(s):
 UCRLPROC206980
TRN: US200807%%735
 DOE Contract Number:
 W7405ENG48
 Resource Type:
 Conference
 Resource Relation:
 Conference: Presented at: 12th National Conference on "Phase Diagrams, Materials Design and its Applications, Shenzhen, China, Oct 24  Oct 28, 2004
 Country of Publication:
 United States
 Language:
 English
 Subject:
 36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALLOYS; DESIGN; ELECTRONIC STRUCTURE; STABILITY; THERMODYNAMICS
Citation Formats
Turchi, P A. THERMODYNAMICS OF MATERIALS: FROM AB INITIO TO PHENOMENOLOGY. United States: N. p., 2004.
Web.
Turchi, P A. THERMODYNAMICS OF MATERIALS: FROM AB INITIO TO PHENOMENOLOGY. United States.
Turchi, P A. 2004.
"THERMODYNAMICS OF MATERIALS: FROM AB INITIO TO PHENOMENOLOGY". United States.
doi:. https://www.osti.gov/servlets/purl/15014609.
@article{osti_15014609,
title = {THERMODYNAMICS OF MATERIALS: FROM AB INITIO TO PHENOMENOLOGY},
author = {Turchi, P A},
abstractNote = {Quantum mechanicalbased (or ab initio) methods are used to predict the stability properties of materials although their application is limited to relatively simple systems in terms of structures and number of alloy components. However thermodynamics of complex multicomponent alloys requires a more versatile approach afforded within the CALPHAD formalism. Despite its success, the lack of experimental data very often prevents the design of robust thermodynamic databases. After a brief survey of ab initio methodologies and CALPHAD, it will be shown how ab initio electronic structure methods can supplement in two ways CALPHAD for subsequent applications. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The other way, more involved, is the assessment of ab initio thermodynamics '{acute a} la CALPHAD'. It will be shown how these results can be used within CALPHAD to predict the equilibrium properties of multicomponent alloys. Finally, comments will be made on challenges and future prospects.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2004,
month = 9
}

Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The other way, more involved, is the assessment of ab initio thermodynamics {acute a} la CALPHAD. It will be shown how these results can be used within CALPHAD to predict the equilibrium properties of multicomponent alloys.

Magnetic materials at finite temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations
We present a unified approach to describe the combined behavior of the atomic and magnetic degrees of freedom in magnetic materials. Using Monte Carlo simulations directly combined with first principles the Curie temperature can be obtained ab initio in good agreement with experimental values. The large scale constrained first principles calculations have been used to construct effective potentials for both the atomic and magnetic degrees of freedom that allow the unified study of influence of phononmagnon coupling on the thermodynamics and dynamics of magnetic systems. The MC calculations predict the specific heat of iron in near perfect agreement with experimentalmore » 
The Computational Modeling of Alloys:From ab initio and thermodynamics to heterogeneous precipitation.
In this lecture we presented a methodology to obtain free energies from empirical potentials and applied it to the study of the phase diagram of FeCr. Subsequently, we used Metropolis Monte Carlo to analyze homogeneous and heterogeneous precipitation of the Cr rich solid solution {alpha}{prime}. These examples are part of our work in the area of steels for nuclear applications and can be found in several publications of our group cited as References. 