First-Principles Calculations of Spinodal Ordering Temperature and Diffuse Intensity Scattering Spectrum for Fe-Pt System

Abstract

First-principles calculations are performed to derive a L1 0 -disorder phase diagram, spinodal ordering temperature and short-range-order diffuse-intensity spectrum for the Fe-Pt system. L1 0 -disorder transition is confirmed to be of the first order by both the temperature dependence of the long-range-order parameter and the large separation between the transition temperature and spinodal ordering temperature. Short-range-order diffuse-intensity maximum appears at AE100ae which is intensified as the spinodal-ordering temperature is approached. The consistency among all these results supports the reliability of the description of the cluster variation free energy used for this study.

Synthetic first-principles studies from phase equilibria to microstructural formation in the Fe-Pt L10 phase

“…Hence, it is inevitable to examine if the homogeneous free energy can reproduce various equilibrium properties and thermal quantities related to phase equilibria such as the transition temperatures. We describe theoretical outline of the first-principles CVM and demonstrate the calculated results of phase stability and phase equilibria for the Fe-Pt system, some of which are reproduced from previous studies [3,27,28] for the sake of completeness. In the latter sections, it is demonstrated how the local free energy described by the firstprinciples CVM can be coarse grained to calculate the time evolution process of APB and APD structures by combining it with PFM.…”

“…Reproduced from Ref. [27] and rearranged. locus of the spinodal ordering temperature [41,42] which is briefly discussed in the following.…”

Time Evolution of Long‐Range Ordering in Fe–Pt Alloys

“…An overview of the literature shows that the main techniques to define a long‐range order (LRO) parameter in Fe–Pt alloys experimentally are electron diffraction, [ 8 ] X‐ray scattering, and Mössbauer spectroscopy. [ 9 ] The current theoretical approaches are based on the first‐principles calculations, [ 10 ] and use computational methods such as MD [ 11 ] and Monte Carlo. [ 12 ]…”

“…At high temperatures, Fe-Pt alloys are disordered with fcc crystal structure in the whole concentration range.An overview of the literature shows that the main techniques to define a long-range order (LRO) parameter in Fe-Pt alloys experimentally are electron diffraction, [8] X-ray scattering, and Mössbauer spectroscopy. [9] The current theoretical approaches are based on the first-principles calculations, [10] and use computational methods such as MD [11] and Monte Carlo. [12] Current research is dedicated to the calculation of the kinetics of the LRO parameter for iron-and platinum-based fcc Fe-Pt alloys.…”

Lattice Statistics and Dynamics within Cluster Variation Method

“…For example, when basic cluster is a pair (tetrahedron) cluster, the approximation is referred to as pair (tetrahedron) approximation. Since the time when Kikuchi 1) had proposed Cluster Variation Method (CVM), various applications of CVM have been proposed such as coherent interface 2) , SRO hardening 3) , effective pair interaction energy 4) , diffuse intensity scattering 5) , phase equilibria and phase diagram [6][7][8][9] , and coupling with PFM 10,11) . In particular, a number of studies for phase diagram calculation [6][7][8] have been conducted because CVM yields more reasonable transformation temperature than Brag-Williams approximation as shown in Ref.…”