Commentary: Recent Advances in Ab Initio Thermodynamics of Materials

The Materials Genome Initiative (MGI)’s goals are to significantly reduce the time and resources necessary to discover, develop, and deploy new materials. Realization of the MGI demands the integration of multiple approaches, spanning advanced simulation, synthesis, and characterization as well as effective informatics approaches. While many initiatives are currently being pursued to address the MGI challenge, the development of new materials solutions to specific technological needs must start by first understanding the phase stability of the material to be developed. This is important not only to assess the feasibility of making the material in the first place but also to understand what changes the material undergoes during processing as well as during operation. Thermodynamics of materials thus lies at the base of any further material development. For almost a century, the phase stability of materials was mostly explored through empirical means. Fifty years ago, within the inorganic materials community, the advent of the calculation of phase diagrams (CALPHAD) method enabled the systematic organization of information about the thermodynamic properties of phases that in turn made possible the prediction of phase diagrams. Within the CALPHAD approach, the thermodynamics of phases are described through mathematical models that are in turn determined by fitting to experimental data. In the past decades, experimental data (phase equilibria, thermochemistry, calorimetry, etc.) has been supplemented by calculations of thermodynamic properties based on so-called first-principles (ab initio) calculations, which are basically methods that solve approximations of the Schrodinger’s equation in which the only information required—within many approximations and parametrizations—is the identity of the atoms as well as their spatial arrangement. While there are still many limitations in these methods (for example, typical uncertainties of a few meV result in differences of tens of Kelvin in relevant temperatures in phase diagrams), first-principles thermodynamic approaches have proven to be remarkably useful, particularly in instances when experimental measurements of thermochemical properties are not available (an increasingly common occurrence) or when the phases that need to be described are not truly thermodynamically stable (but whose description is necessary within the CALPHAD formalism) and cannot be characterized through experimental means. In this technical topic, we have collected a series of articles that illustrate some of the most recent advances in the use of first-principles methods to describe the thermodynamic properties of materials. Examples are presented of recent theoretical and computational techniques to predict thermodynamic properties, to search ground states, and to integrate first-principles thermodynamics to CALPHAD assessments. Also presented are some more specialized examples in which first-principles methods have been used to describe the phase stability of complex materials. In their article, ‘‘Materials Design and Discovery with High-Throughput Density Functional Theory: The Open Quantum Materials Database (OQMD),’’ James Saal and collaborators present the recent development of the Open Quantum Materials Database (OQMD), which combines highly accurate high-throughput DFT calculations—based on crystal structures reported in the inorganic crystal structure database (ICSD) as well as derived Raymundo Arroyave is the Chair of and JOM advisor for the Alloy Phases Committee of the TMS Electronic, Magnetic, & Photonic Materials Division and the Structural Materials Division; and the guest editor for the topic Recent Advances in Ab Initio Thermodynamics of Materials in this issue. JOM, Vol. 65, No. 11, 2013