Research Projects

The Center for Next Generation of Materials Design is specifically designed to overcome four critical scientific gaps to make computational materials design a robust everyday tool that delivers new functional materials. These gaps are in the areas of multiple-property design, accuracy and relevance, metastability, and synthesizability.

Our research program centers around six highly collaborative projects (P1–P5, P8) that are designed to explore materials by design and address the goals of the EFRC. Each of the projects involves a multi-disciplinary approach integrating theory with advanced experimentation. We also have two projects (P6, P7) on outreach/dissemination and cross-cutting foundational tool development.

See Publications for a listing of publications and CNGMD highlights categorized by project.

Project 1—Ternary Pnictides Search

Nitride- and phosphide-based pnictides have been relatively underexplored for energy applications. Our EFRC team has initiated a broad search for new ternary pnictides with useful optoelectronic properties combining high-throughput computation with combinatorial synthesis to discover previously unreported pnictides, and explore their optoelectronic and semiconductor properties. Among the pnictides (Pn = N, P, As, Sb, Bi), the nitrides are an interesting family of compounds because of their mixed covalent/ionic bonding properties. Nitrides also offer an excellent opportunity to study metastability, as suggested by more positive formation enthalpies of nitrides compared to oxides.

Project 2—Polymorphs and Synthesizability

We are taking a multipronged approach to enable the design of metastable polymorphic materials, i.e. those above the convex hull. We seek new functionality through the ability to target the synthesis of specific polymorphs that are close in energy (formation enthalpy).  We aim to develop first-principles, high-throughput computational tools to predict the functionality and formation energy of specific polymorphs, including new unknown structures and to develop experimental approaches to realize those polymorphs. This work requires us to identify the manifold of polymorphs at a particular composition, to predict structure and functionality for each, to determine synthesis approaches for targeting a particular polymorph, and to understand transformational pathways between polymorphs. This work is tightly coupled to experimental efforts in the targeted growth of specific polymorphs via solution phase and gas phase deposition methods. We are focusing on V-O, Mn-O, and Ti-O based systems, which are known to show diverse functionality with a range of known polymorphs and have potential for a number of energy technology applications including energy storage, catalysts, switches, electrodes, and electrochromic windows.

Project 3—Chalcogenide Alloys

Alloys and solid solutions are a particularly important class of materials for design and discovery, as their properties can often be tailored in a continuous fashion. For example, the precise control of the band gap energy as a function of the composition of InGaN and AlGaN alloys in light emitting diodes (LED) has enabled the LED lighting revolution. In semiconductors and optoelectronic materials, the systematic study of alloys has been restricted mostly to isostructural alloys in Group IV (e.g., SiGe), III-V (e.g., InGaN), and II-VI (E.g., CdZnTe) semiconductor systems.

In this EFRC, we extend materials design to the more general case of heterostructural semiconductor alloys, i.e., the case where the alloy constituents have different crystal structures. This increased complexity creates more challenges, but also open new opportunities for materials by design. Our objective is to generate the scientific knowledge needed to master the controlled synthesis of heterostructural semiconductor alloys with desirable properties. Our approach couples alloy theory based on first principles calculations (DFT, GW, RPA total energies with a range of different thin-film synthesis and characterization techniques (using RF sputtering, PLD, ALD, and combinatorial methods), which are particularly suited for the deposition of metastable non-equilibrium phases.

Project 4—Defect Phase Diagrams

One of the key types of metastability is manifested by defects where local non-equilibrium effects can profoundly alter the properties of materials without changing their crystal structure or chemical composition. The influences of defects in bulk phases and at interfaces are often enabling for increasing conductivity through doping. In this project our goal is to develop a defect phase diagram to include both simple defects and associated defects. We are coupling enhanced DFT with atomistic molecular dynamic simulations to handle more complex defect pairs and clusters. We are verifying these theoretical results by synthesis and characterization experiments. We have chosen to investigate the defect phase diagram for Ga2O3 both because of its increasing relevancy in photovoltaics and wide bandgap electronics and because doping it to sufficient levels, remains a challenge.

Project 5—Perovskite-Inspired Search Project

Methylammonium lead halide (MAPbX3) perovskites have created substantial excitement with their unprecedented rapid rise in photovoltaic efficiencies that have gone from less than 4% to more than 20% in only a few years. The goals of this CNGMD project are to: 1) identify the material properties that confer exceptional minority-carrier lifetimes to the MAPbX3 perovskites which is the key distinguishing parameter enabling high solar cell efficiencies; and 2) predict and synthesize materials that exhibit similar material properties, testing our hypothesis that MAPbX3 is not unique. We show below that an integrated approach using theory, data mining and experiment provides important information on the key features of these materials and leads to the identification of new classes of materials with potential enhanced functionality for photovoltaics.

Project 6—Outreach and Communications

We are involved in MRS Meeting Symposia, seminars, and talks and have produced a video on the Center.

External Collaboration with: EFRC Center for the Computational Design of Functional Layered Materials, EFRC Center for Excitonics, The Materials Project, Helmholtz Center Berlin, and Helmholtz Zentrum.

Project 7—Foundational Tools

Our EFRC team has substantial core competence in theory, synthesis, and characterization, particularly for semiconductor and optoelectronic materials, that spans from high throughput and combinatorial approaches to very detailed and sophisticated studies.  Our theorists have ready access to world-class supercomputing facilities (e.g. NERSC, NREL Peregrine) and a number of local clusters as well as capabilities they have developed for high throughput computational and workflows (e.g. Pymatgen at LBNL and Pylada at NREL).  We also have developed databases, analysis tools and data mining for the enormous quantity of experimental and theoretical data.

The CNGMD makes extensive use of the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC. The brightness and tunability of synchrotron sources makes them well suited for studying systems in-situ and operando. For in-situ monitoring crystallization of amorphous films or recrystallization of samples we access two different time scales at SSRL. The CNGMD has also utilized the Advanced Photon Source (APS) at the Argonne National Lab, since this complements experiments done at SLAC through access to higher X-ray energies.

In addition to tools developed for specific projects, we are developing several cross-cutting experimental and theory tools.

    • In-situ X-ray diffraction and absorption spectroscopy during solution synthesis
    • Combinatorial nitride deposition system
    • Temperature-dependent Hall effect mapping system
    • In-situ conductivity measurement during thermal annealing
    • Dynamic atom probe tomography
    • JVTI: voltage (V), temperature (T), injection-level (I) dependent current

 

Project 8—Polar Materials