Predicting the Phase Stability of Multicomponent High-Entropy Compounds

Abstract

A generic method to estimate the relative feasibility of formation of high-entropy compounds in a single phase, directly from first principles, is developed. As a first step, the relative formation abilities of 56 multicomponent, AO, oxides were evaluated. These were constructed from five cation combinations chosen from A = {Ca, Co, Cu, Fe, Mg, Mn, Ni, Zn}. Candidates for multicomponent oxides are predicted from descriptors related to the enthalpy and configurational entropy obtained from the mixing enthalpies of two-component oxides. The utility of this approach is evaluated by comparing the predicted combinations with the experimentally realized entropy-stabilized oxide, (MgCoCuNiZn)­O. In the second step, Monte Carlo simulations are utilized to investigate the phase composition and local ionic segregation as a function of temperature. This approach allows for the evaluation of potential secondary phases, thereby making realistic predictions of novel multicomponent compounds that can be synthesized.

Computationally accelerated discovery of high entropy pyrochlore oxides

“…La and Nd, we find that 10 compounds are stable as pyrochlore, 6 as PRLO, 8 as LaTaO 4 (NdTaO 4 ), one and two component combinations in their ground states, are much smaller than the mixing enthalpies of the AO type binary oxides as shown in Figure 2 of Ref. [19], indicating that -in this case -the structures with two cation sublattices are thermodynamically more stable than the structures with only one cation sublattice. This is due to the large contribution of the lattice enthalpy generated from the ordering of the A− and B−site cations in the ternary oxide super lattice.…”

“…In our previous study, exploring the formation ability of five component divalent cations in the rock salt structure, we developed and discussed a set of thermodynamic descriptors based on the mixing enthalpies of two component oxides [19]. This approach allowed us to quickly screen the five component oxides directly from DFT calculations -without the high computational costs and configurational sampling, associated with large finite sized super cells.…”

“…, is used to describe the interaction energy between B − B cations in phase P , ∆H B−B mix = ∆H mix A 2 (BB ) 2 O n , P in the five component oxide (FCO), as described in our previous work [19]. La and Nd, we find that 10 compounds are stable as pyrochlore, 6 as PRLO, 8 as LaTaO 4 (NdTaO 4 ), one and two component combinations in their ground states, are much smaller than the mixing enthalpies of the AO type binary oxides as shown in Figure 2 of Ref.…”

“…This is due to the large contribution of the lattice enthalpy generated from the ordering of the A− and B−site cations in the ternary oxide super lattice. We utilize the values of these mixing enthalpies as parameters in the nearest neighbor model to estimate the thermodynamic descriptors by systematically exploring local configurations as discussed in our previous work on high entropy oxides in rock salt structure [19].…”

“…In our previous work on predicting high entropy oxides in the rock salt structure [19], we have demonstrated that the enthalpy and entropy descriptors, m and σ, respectively, influence the formation ability of a multi-component, single phase structure [40]. The expressions for calculating the values of m and σ are given in Eq.…”