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Two high-pressure insulating phases of lithium were predicted using random search and evolutionary algorithm methods with first-principles electronic structure calculations. It is shown that lithium will transform from the metallic cubic cI16 phase to an insulating monoclinic C2 structure at 74 GPa. The C2 structure is the most stable phase up to 91 GPa,(More)
High-pressure phase transformations of Ca are studied using the metadynamics method to explore the anharmonic free-energy surface, together with a genetic algorithm structural search method to identify lowest enthalpy structures. Disagreement between theory and experiment regarding the structure of Ca in the pressure range 32-119 GPa is partially resolved(More)
The high-pressure behavior of silane, SiH(4), plus molecular hydrogen was investigated using a structural search method and ab initio molecular dynamics to predict the structures and examine the physical origin of the pressure-induced drop in hydrogen intramolecular vibrational (vibron) frequencies. A structural distortion is predicted at 15 GPa from a(More)
The search for stable polymeric nitrogen and polynitrogen compounds has attracted great attention due to their potential applications as high-energy-density materials. Here we report a theoretical prediction of an interesting LiN5 crystal through first-principles calculations and unbiased structure searching techniques. Theoretical calculations reveal that(More)
Pressure-induced metallization and potential superconductivity of BeH2 has been a topic of interest. In the present study, we extensively explored the crystal structures of BeH2 in a wide pressure range of 0-300 GPa using an unbiased structure searching method coupled with first-principles density functional calculations. A series of pressure-induced(More)
Molecular and crystalline structures of (BH(3))(n) have been theoretically studied in the pressure regime from 1 atm to 100 GPa. At lower pressures, crystals of the familiar molecular dimer are the structure of choice. At 1 atm, in addition to the well-characterized β diborane structure, we suggest a new polymorph of B(2)H(6), fitting the diffraction lines(More)
New polynitrides containing metastable forms of nitrogen are actively investigated as potential high-energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN3, we identified five new stoichiometric(More)
A combined theoretical and experimental study of lithium palladium deuteride (Li2PdD2) subjected to pressures up to 50 GPa reveals one structural phase transition near 10 GPa, detected by synchrotron powder x-ray diffraction, and metadynamics simulations. The ambient-pressure tetragonal phase of Li2PdD2 transforms into a monoclinic C2/m phase that is(More)
Multiferroics have been of interest as materials for use in data storage due to their coexisting ferroelectric and ferromagnetic properties. The properties of cupric oxide have been studied at pressures below 70 GPa, and it has even been suggested that it may be a room temperature multiferroic at pressures of 20 to 40 GPa. However, the properties of cupric(More)