Abstract
A thorough in situ characterization of materials at extreme conditions is challenging, and computational tools such as crystal structural search methods in combination with ab initio calculations are widely used to guide experiments by predicting the composition, structure, and properties of high-pressure compounds. However, such techniques are usually computationally expensive and not suitable for large-scale combinatorial exploration. On the other hand, data-driven computational approaches using large materials databases are useful for the analysis of energetics and stability of hundreds of thousands of compounds, but their utility for materials discovery is largely limited to idealized conditions of zero temperature and pressure. Here, we present a novel framework combining the two computational approaches, using a simple linear approximation to the enthalpy of a compound in conjunction with ambient-conditions data currently available in high-throughput databases of calculated materials properties. We demonstrate its utility by explaining the occurrence of phases in nature that are not ground states at ambient conditions and estimating the pressures at which such ambient-metastable phases become thermodynamically accessible, as well as guiding the exploration of ambient-immiscible binary systems via sophisticated structural search methods to discover new stable high-pressure phases.
Highlights
The laws of thermodynamics dictate that only compounds corresponding to global minima of the Gibbs free energy for a given set of external conditions are viable ground states with infinite lifetimes [1]
A special case of this design procedure is to choose a set of thermodynamic parameters such that the desired phase becomes the thermodynamic ground state at the chosen conditions, where it forms at equilibrium and can be recovered as a metastable phase at ambient conditions if all transition barriers leading away from it are sufficiently high [6]
Using the implicitly available high-pressure information in a HT-density functional theory (DFT) database, the Open Quantum Materials Database (OQMD), together with a simple approximation to the formation enthalpy of a compound, we study the effect of pressure on the thermodynamic scale of stability or metastability of inorganic compounds
Summary
The laws of thermodynamics dictate that only compounds corresponding to global minima of the Gibbs free energy for a given set of external conditions are viable ground states with infinite lifetimes [1]. For such materials, there always exists a synthetic route that follows an overall exothermic chemical reaction pathway, and all systems at finite temperature will attain a Boltzmann distribution with a high occupation of the ground state in thermodynamic equilibrium. Materials in many industrially relevant applications are metastable; i.e., they have higher energies than the equilibrium ground states A special case of this design procedure is to choose a set of thermodynamic parameters such that the desired phase becomes the thermodynamic ground state at the chosen conditions, where it forms at equilibrium and can be recovered as a metastable phase at ambient conditions if all transition barriers leading away from it are sufficiently high [6]
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