Thermodynamic Analysis of Steels by Incorporating First-Principles Calculations into the CALPHAD Approach

2007 ◽  
Vol 539-543 ◽  
pp. 2413-2418 ◽  
Author(s):  
Hiroshi Ohtani ◽  
N. Hanaya ◽  
Mitsuhiro Hasebe
Keyword(s):  
Phase Diagrams ◽  
Thermodynamic Analysis ◽  
First Principles ◽  
Experimental Information ◽  
Full Potential ◽  
Calphad Approach ◽  
First Principles Calculations ◽  
Plane Wave Method ◽  
Ternary Phase Diagrams ◽  
High Degree

A thermodynamic analysis of the Fe−M−P (M = Nb, Ti) ternary system has been performed by combining first-principles calculations with the CALPHAD approach. Because of the lack of experimental information available, thermodynamic properties of orthorhombic anti-PbCl2-type FeMP were evaluated using the Full Potential Linearized Augmented Plane Wave method, and the estimated values were introduced into a CALPHAD-type thermodynamic analysis. Applying this procedure, the phase diagrams of the Fe−M−P ternary phase diagrams whose contents are uncertain so far were calculated with a high degree of probability. Phase diagrams for high-purity ferritic stainless steels obtained following the same procedure are also presented.

Thermodynamic Analysis of the Ti-Zr-H Ternary Phase Diagram

2007 ◽  
Vol 26-28 ◽  
pp. 989-992 ◽  
Author(s):  
Shusuke Ukita ◽  
Hiroshi Ohtani ◽  
Mitsuhiro Hasebe
Keyword(s):  
Ternary Compound ◽  
Thermodynamic Analysis ◽  
Binary Systems ◽  
Ternary Phase Diagram ◽  
Thermodynamic Description ◽  
Experimental Information ◽  
Full Potential ◽  
Calphad Approach ◽  
Plane Wave Method ◽  
Linearized Augmented Plane Wave

A thermodynamic analysis of the Ti-Zr-H ternary system has been performed by combining first-principles calculations with the CALPHAD approach. To enable the thermodynamic description of the binary systems, the results from our previous evaluation were adopted for the Ti-H, Zr-H, and Ti-Zr systems. The ternary compound, Ti2ZrH4, with an Fd3m-type crystal structure, exists over a wide composition range, and the (Ti)2(Zr)1(H,Va)4-type three-sublattice model was applied to describe its thermodynamic properties. Because of the lack of experimental information available, the enthalpy of formation of the Ti2ZrH4 phase was evaluated using the Full Potential Linearized Augmented Plane Wave method, and the estimated values were introduced into a CALPHAD-type thermodynamic analysis with some other experimental information. The calculated phase diagrams and the hydrogen isotherms were in good accordance with previous experimental results. Our calculations revealed that the ternary compound decomposes into a bcc and gas phase in the vicinity of 1270 K.

Thermodynamic analysis of the Fe–Ti–P ternary system by incorporating first-principles calculations into the CALPHAD approach

Calphad ◽  
2006 ◽  
Vol 30 (2) ◽  
pp. 147-158 ◽  
Author(s):  
Hiroshi Ohtani ◽  
Naoko Hanaya ◽  
Mitsuhiro Hasebe ◽  
Shin-ichi Teraoka ◽  
Masayuki Abe
Keyword(s):  
Ternary System ◽  
Thermodynamic Analysis ◽  
First Principles ◽  
Calphad Approach ◽  
First Principles Calculations

scholarly journals Energetics and phase diagrams of Fe-Cr and Co-Cr systems from first principles

2002 ◽  
Vol 38 (3-4) ◽  
pp. 205-211 ◽  
Author(s):  
J. Vrestzál ◽  
J. Houserová ◽  
M. Sob
Keyword(s):  
Phase Diagrams ◽  
First Principles ◽  
Thermodynamic Description ◽  
Full Potential ◽  
Augmented Plane Wave ◽  
New Model ◽  
Plane Wave Method ◽  
Physical Information ◽  
Total Energies ◽  
End Members

The first principles computations of the total energies of complex phases have been addressed recently. The structural energy differences, calculated by FLAPW (Full potential augmented plane wave) method, enable us to utilize a more complete physical information about total energy of intermetallic phases and to propose a new model for their thermodynamic description. Our approach is based on the two-sublattice model, similarly as for solid solution phases, but the structural energy differences for end-members in the metastable or unstable structures are obtained by means of first-principles electronic structure calculations. Phase diagrams of Fe-Cr and Co-Cr systems containing the intermetallic sigma-phase (5 inequivalent lattice sites, 30 atoms in repeat cell) are described here as an example of application of our new model.

scholarly journals Thermodynamic modeling of the Na-X (X = Si, Ag, Cu, Cr) systems

2012 ◽  
Vol 48 (2) ◽  
pp. 273-282 ◽  
Author(s):  
D. Hao ◽  
M. Bu ◽  
Y. Wang ◽  
Y. Tang ◽  
Q. Gao ◽  
...  
Keyword(s):  
Low Temperature ◽  
Thermodynamic Modeling ◽  
First Principles ◽  
Binary Systems ◽  
Experimental Information ◽  
Enthalpies Of Formation ◽  
Calphad Approach ◽  
First Principles Calculations ◽  
Self Consistent ◽  
Measured Phase

The Na-X (X = Si, Ag, Cu, Cr) systems have been critically reviewed and modeled by means of the CALPHAD approach. The two compounds, NaSi and Ag2Na, are treated as stoichiometric ones. By means of first-principles calculations, the enthalpies of formation at 0 K for the LT-NaSi (low temperature form of NaSi) and Ag2Na have been computed to be -5210 and -29821.8 Jmol-1, respectively, with the desire to assist thermodynamic modeling. One set of self-consistent thermodynamic parameters is obtained for each of these binary systems. Comparisons between calculated and measured phase diagrams show that most of the experimental information can be satisfactorily accounted for by the present thermodynamic descriptions.

First-Principles Studies of the Magnetic Properties of hcp Cr in Cr/Cu(111) and Cr/Ru(0001) Superlattices

2002 ◽  
Vol 721 ◽  
Author(s):  
G. Y. Guo
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Recent Observation ◽  
Theoretical Calculations ◽  
Ferromagnetic State ◽  
Full Potential ◽  
Generalized Gradient ◽  
Plane Wave Method ◽  
Wide Range ◽  
Linearized Augmented Plane Wave

AbstractLatest first-principles density functional theoretical calculations using the generalized gradient approximation and highly accurate all-eleectron full-potential linearized augmented plane wave method, show that bulk hcp Cr would be a paramagnet and that no ferromagnetic state could be stabilized over a wide range of volume [1]. To understand the recent observation of the weakly ferromagnetic state of Cr in hcp Cr/Ru (0001) superlattices [2], the same theoretical calculations have been carried out for the hcp Cr3/Ru7 (0001) and hcp Cr3/fcc Cu6 (111) superlattices. The Cr/Ru superlattice is found to be ferromagnetic with a small magnetic moment of ∼0.31μB/Cr while in contrast, Cr/Cu superlattice is found to be nonmagnetic.

First-principles calculations of electronic and magnetic properties of XMn2Y2 (X = Ca, Sr; Y = Sb, Bi) compounds

2019 ◽  
Vol 33 (18) ◽  
pp. 1950199
Author(s):  
Zeshan Zada ◽  
A. Laref ◽  
G. Murtaza ◽  
Aurang Zeb ◽  
A. Yar
Keyword(s):  
Magnetic Properties ◽  
First Principles ◽  
Full Potential ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Spin Configuration ◽  
Augmented Plane Wave ◽  
Electronic And Magnetic Properties ◽  
Magnetic Stability ◽  
Linearized Augmented Plane Wave

We have examined the magnetic stability; antiferromagnetic (AFM) ordering; electronic and magnetic properties of composition XMn2Y2 (X = Ca, Sr; Y = Sb, Bi) using framework of full-potential linearized augmented plane wave (FP-LAPW) method within generalized gradient (PBE-GGA) approximations in AFM phase. We have specified that AFM state is most suitable for these compounds as compared to other configurations at their relaxed lattice parameters. An AFM spin configuration of Mn atoms is shown to be impressive state for these compounds. Based on its electronic properties, these compounds have a metallic nature in Paramagnetic (PM) but in AFM phase it shows different nature from PM phase. From a suitable phase, it has been cleared that both Mn atoms well-adjusted antiferromagnetically.

First-principles calculations to investigate structural, electronic and optical properties of (ZnSe)n/(ZnTe)n superlattices

2020 ◽  
Author(s):  
Messaoud Caid
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Correlation Energy ◽  
Local Density ◽  
Full Potential ◽  
First Principles Calculations ◽  
Electronic And Optical Properties ◽  
Lmto Method ◽  
Binary Compounds

An investigation into the structural, electronic and optical properties of superlattices(SLs) (ZnSe)n/(ZnTe)n was conducted using first principles calculations based on density functional theory (DFT). The total energies were calculated within the full-potential linear muffin-tin orbital (FP-LMTO) method augmented by a plane-wave basis (PLW), implemented in LmtART 7.0 code. The effects of the approximations to the exchange-correlation energy were treated by the local density approximation (LDA). The ground state properties of (ZnSe)n/(ZnTe)n binary compounds are determined and compared with the available data. It is found that the superlattice (n-n: 1-1, 2-2 and 3-3) band gaps vary depending on the layers used. The optical constants, including the dielectric function ε(w), the refractive index n(w) and the reflectivity R(w), are calculated for radiation energies up to 35eV.

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