Metallization of Hydrogen-Rich Materials: Predicting Novel Superconductors

TECHNICAL SUMMARY The Division of Materials Research and the Office of Cyberinfrastrcture contribute funds to this award. It supports theoretical research and education which will lead towards the rational design of novel superconductors. It is thought that under sufficient compression hydrogen will become metallic due to the pressure-induced broadening of filled and unfilled bands, and their eventual overlap. Theoretical predictions indicate that this phase may be a high temperature superconductor. Unfortunately, hydrogen does not become metallic at the highest static pressures reached so far. There is now tremendous interest in developing chemically inspired strategies which could significantly decrease the pressure necessary for metallization. Two examples are: combination with tetravalent atoms, as in the group 14 hydrides, or by the addition of an electropositive element. The PI will focus on predicting the structures of ionic and covalent polyhydrides with unusual stoichiometries that are stable, and metallic under pressure. An evolutionary algorithm, interfaced with a first-principles electronic structure program will be employed towards this end. Already, theoretical and experimental research has shown that specific lithium and silicon bearing hydrogen materials become stable when squeezed, and it is likely that they are metals at experimentally achievable pressures. This work will lead to a deeper understanding of the chemistry, electronic structure and potential superconductivity of hydrogen-rich materials under pressure. The PI aims to determine which factors are important in facilitating the metallization of these systems under mild compression, determine the most favorable stoichiometries and structures, their properties, and ways to chemically stabilize these phases at commercially accessible pressures. The PI will develop an evolutionary algorithm, XtalOpt, which will be used to predict the structures of the most stable systems. This algorithm will be made freely available to the materials science, physics and chemistry communities as an extension to the free visualization tool "Avogadro." It will be released under the GNU Public License, and interfaced with several electronic structure packages which are widely used to study solids. The code will make use of already existing cyberinfrastructure, and will be highly modular, and clearly documented so as to facilitate further development. NONTECHNICAL SUMMARY The Division of Materials Research and the Office of Cyberinfrastrcture contribute funds to this award. It supports theoretical research and education whose ultimate goal is to use concepts, and theoretical and computational techniques to design new superconducting materials. In a superconductor electric current can flow without dissipation. Replacing copper wires with high temperature superconducting power lines could have a tremendous impact on the electrical power infrastructure of the USA. Unfortunately, all of the materials which are known to behave as superconductors do so only at very low temperatures. Theoretical work has predicted that under pressure the simplest element hydrogen will become metallic, and superconducting near room temperature. Unfortunately, the pressures necessary to metalize hydrogen are greater than those at the center of the earth. The PI will develop chemically inspired strategies which could significantly decrease the pressure necessary to achieve metallic hydrogen. State-of-the-art computational techniques will be employed to predict the structures and properties of hydrogen rich systems under pressure. The PI's computations will determine if these materials could potentially be superconductors, and will suggest how these phases may be chemically stabilized at normal pressures. An evolutionary algorithm, XtalOpt, will be developed in order to predict the structures of the most stable systems. This algorithm will be made freely available to the materials science, physics and chemistry communities as an extension to the free visualization tool "Avogadro." It will be released under the GNU Public License, and interfaced with several computer programs which are widely used to study solid state materials.