The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Burkhard Militzer - One of the best experts on this subject based on the ideXlab platform.

  • prediction of chlorine and fluorine crystal structures at high pressure using symmetry driven structure search with geometric constraints
    Journal of Chemical Physics, 2020
    Co-Authors: Mark A Olson, Shefali Bhatia, Paul B Larson, Burkhard Militzer
    Abstract:

    The high-pressure properties of fluorine and chlorine are not yet well understood because both are highly reactive and volatile elements, which have made conducting diamond anvil cell and x-ray diffraction experiments a challenge. Here, we use ab initio methods to search for stable crystal structures of both elements at megabar pressures. We demonstrate how symmetry and geometric constraints can be combined to efficiently generate crystal structures that are composed of diatomic molecules. Our algorithm extends the symmetry driven structure search method [R. Domingos et al., Phys. Rev. B 98, 174107 (2018)] by adding constraints for the bond length and the number of atoms in a molecule while still maintaining generality. As a method of validation, we have tested our approach for dense hydrogen and reproduced the known molecular structures of Cmca-12 and Cmca-4. We apply our algorithm to study chlorine and fluorine in the pressure range of 10 GPa–4000 GPa while considering crystal structures with up to 40 atoms per unit cell. We predict chlorine to follow the same series of phase transformations as elemental iodine from Cmca to Immm to Fm3¯m, but at substantially higher pressures. We predict fluorine to transition from a C2/c to Cmca structure at 70 GPa, to a novel orthorhombic and metallic structure with P42/mmc symmetry at 2500 GPa, and finally to its cubic analog form with Pm3¯n symmetry at 3000 GPa.

  • prediction of chlorine and fluorine crystal structures at high pressure using symmetry driven structure search with geometric constraints
    arXiv: Materials Science, 2020
    Co-Authors: Mark A Olson, Shefali Bhatia, Paul B Larson, Burkhard Militzer
    Abstract:

    The high-pressure properties of fluorine and chlorine are not yet well understood because both are highly reactive and volatile elements, which has made conducting diamond anvil cell and x-ray diffraction experiments a challenge. Here we use ab initio methods to search for stable crystal structures of both elements at megabar pressures. We demonstrate how symmetry and geometric constraints can be combined to efficiently generate crystal structures that are composed of diatomic molecules. Our algorithm extends the symmetry driven structure search method [Phys. Rev. B 98 (2018) 174107] by adding constraints for the bond length and the number of atoms in a molecule, while still maintaining generality. As a method of validation, we have tested our approach for dense hydrogen and reproduced the known molecular structures of Cmca-12 and Cmca-4. We apply our algorithm to study chlorine and fluorine in the pressure range from 10--4000 GPa while considering crystal structures with up to 40 atoms per unit cell. We predict chlorine to follow the same series of phase transformations as elemental iodine from Cmca to Immm to Fm$\bar{3}$m, but at substantially higher pressures. We predict fluorine to transition from a C2/c to an Cmca structure at 70 GPa, to a novel orthorhombic and metallic structure with P$4_2$/mmc symmetry at 2500 GPa, and finally into its cubic analogue form with Pm$\bar{3}$n symmetry at 3000 GPa.

Marvin L Cohen - One of the best experts on this subject based on the ideXlab platform.

  • theoretical prediction of the high pressure phase ge Cmca
    Physical Review B, 2000
    Co-Authors: Filipe J Ribeiro, Marvin L Cohen
    Abstract:

    Ab initio pseudopotential total energy density-functional theory--local-density approximation calculations were performed to study the crystalline structures of Ge under pressure. Following the well established sequence of structural phases $(\mathrm{diamond}\ensuremath{\rightarrow}\ensuremath{\beta}\ensuremath{-}\mathrm{Sn}\ensuremath{\rightarrow}\mathrm{Imm}\stackrel{\ensuremath{\rightarrow}}{a}\mathrm{sh})$ under increasing pressure, we predict a transition into a new phase, with $\mathrm{Cmca}$ space-group symmetry, at $90\ifmmode\pm\else\textpm\fi{}2 \mathrm{GPa}.$ We estimate the superconducting transition temperature ${T}_{c}$ for this phase to be in the range 2 to 7 K, the same range obtained previously by detailed calculations for the Ge-sh phase. The $\mathrm{Cmca}$ phase should remain stable up to $137\ifmmode\pm\else\textpm\fi{}10$ GPa where a transition to the hcp structure is predicted to occur. The same path is followed by Si although at lower pressures.

Mark A Olson - One of the best experts on this subject based on the ideXlab platform.

  • prediction of chlorine and fluorine crystal structures at high pressure using symmetry driven structure search with geometric constraints
    Journal of Chemical Physics, 2020
    Co-Authors: Mark A Olson, Shefali Bhatia, Paul B Larson, Burkhard Militzer
    Abstract:

    The high-pressure properties of fluorine and chlorine are not yet well understood because both are highly reactive and volatile elements, which have made conducting diamond anvil cell and x-ray diffraction experiments a challenge. Here, we use ab initio methods to search for stable crystal structures of both elements at megabar pressures. We demonstrate how symmetry and geometric constraints can be combined to efficiently generate crystal structures that are composed of diatomic molecules. Our algorithm extends the symmetry driven structure search method [R. Domingos et al., Phys. Rev. B 98, 174107 (2018)] by adding constraints for the bond length and the number of atoms in a molecule while still maintaining generality. As a method of validation, we have tested our approach for dense hydrogen and reproduced the known molecular structures of Cmca-12 and Cmca-4. We apply our algorithm to study chlorine and fluorine in the pressure range of 10 GPa–4000 GPa while considering crystal structures with up to 40 atoms per unit cell. We predict chlorine to follow the same series of phase transformations as elemental iodine from Cmca to Immm to Fm3¯m, but at substantially higher pressures. We predict fluorine to transition from a C2/c to Cmca structure at 70 GPa, to a novel orthorhombic and metallic structure with P42/mmc symmetry at 2500 GPa, and finally to its cubic analog form with Pm3¯n symmetry at 3000 GPa.

  • prediction of chlorine and fluorine crystal structures at high pressure using symmetry driven structure search with geometric constraints
    arXiv: Materials Science, 2020
    Co-Authors: Mark A Olson, Shefali Bhatia, Paul B Larson, Burkhard Militzer
    Abstract:

    The high-pressure properties of fluorine and chlorine are not yet well understood because both are highly reactive and volatile elements, which has made conducting diamond anvil cell and x-ray diffraction experiments a challenge. Here we use ab initio methods to search for stable crystal structures of both elements at megabar pressures. We demonstrate how symmetry and geometric constraints can be combined to efficiently generate crystal structures that are composed of diatomic molecules. Our algorithm extends the symmetry driven structure search method [Phys. Rev. B 98 (2018) 174107] by adding constraints for the bond length and the number of atoms in a molecule, while still maintaining generality. As a method of validation, we have tested our approach for dense hydrogen and reproduced the known molecular structures of Cmca-12 and Cmca-4. We apply our algorithm to study chlorine and fluorine in the pressure range from 10--4000 GPa while considering crystal structures with up to 40 atoms per unit cell. We predict chlorine to follow the same series of phase transformations as elemental iodine from Cmca to Immm to Fm$\bar{3}$m, but at substantially higher pressures. We predict fluorine to transition from a C2/c to an Cmca structure at 70 GPa, to a novel orthorhombic and metallic structure with P$4_2$/mmc symmetry at 2500 GPa, and finally into its cubic analogue form with Pm$\bar{3}$n symmetry at 3000 GPa.

Filipe J Ribeiro - One of the best experts on this subject based on the ideXlab platform.

  • theoretical prediction of the high pressure phase ge Cmca
    Physical Review B, 2000
    Co-Authors: Filipe J Ribeiro, Marvin L Cohen
    Abstract:

    Ab initio pseudopotential total energy density-functional theory--local-density approximation calculations were performed to study the crystalline structures of Ge under pressure. Following the well established sequence of structural phases $(\mathrm{diamond}\ensuremath{\rightarrow}\ensuremath{\beta}\ensuremath{-}\mathrm{Sn}\ensuremath{\rightarrow}\mathrm{Imm}\stackrel{\ensuremath{\rightarrow}}{a}\mathrm{sh})$ under increasing pressure, we predict a transition into a new phase, with $\mathrm{Cmca}$ space-group symmetry, at $90\ifmmode\pm\else\textpm\fi{}2 \mathrm{GPa}.$ We estimate the superconducting transition temperature ${T}_{c}$ for this phase to be in the range 2 to 7 K, the same range obtained previously by detailed calculations for the Ge-sh phase. The $\mathrm{Cmca}$ phase should remain stable up to $137\ifmmode\pm\else\textpm\fi{}10$ GPa where a transition to the hcp structure is predicted to occur. The same path is followed by Si although at lower pressures.

Shefali Bhatia - One of the best experts on this subject based on the ideXlab platform.

  • prediction of chlorine and fluorine crystal structures at high pressure using symmetry driven structure search with geometric constraints
    Journal of Chemical Physics, 2020
    Co-Authors: Mark A Olson, Shefali Bhatia, Paul B Larson, Burkhard Militzer
    Abstract:

    The high-pressure properties of fluorine and chlorine are not yet well understood because both are highly reactive and volatile elements, which have made conducting diamond anvil cell and x-ray diffraction experiments a challenge. Here, we use ab initio methods to search for stable crystal structures of both elements at megabar pressures. We demonstrate how symmetry and geometric constraints can be combined to efficiently generate crystal structures that are composed of diatomic molecules. Our algorithm extends the symmetry driven structure search method [R. Domingos et al., Phys. Rev. B 98, 174107 (2018)] by adding constraints for the bond length and the number of atoms in a molecule while still maintaining generality. As a method of validation, we have tested our approach for dense hydrogen and reproduced the known molecular structures of Cmca-12 and Cmca-4. We apply our algorithm to study chlorine and fluorine in the pressure range of 10 GPa–4000 GPa while considering crystal structures with up to 40 atoms per unit cell. We predict chlorine to follow the same series of phase transformations as elemental iodine from Cmca to Immm to Fm3¯m, but at substantially higher pressures. We predict fluorine to transition from a C2/c to Cmca structure at 70 GPa, to a novel orthorhombic and metallic structure with P42/mmc symmetry at 2500 GPa, and finally to its cubic analog form with Pm3¯n symmetry at 3000 GPa.

  • prediction of chlorine and fluorine crystal structures at high pressure using symmetry driven structure search with geometric constraints
    arXiv: Materials Science, 2020
    Co-Authors: Mark A Olson, Shefali Bhatia, Paul B Larson, Burkhard Militzer
    Abstract:

    The high-pressure properties of fluorine and chlorine are not yet well understood because both are highly reactive and volatile elements, which has made conducting diamond anvil cell and x-ray diffraction experiments a challenge. Here we use ab initio methods to search for stable crystal structures of both elements at megabar pressures. We demonstrate how symmetry and geometric constraints can be combined to efficiently generate crystal structures that are composed of diatomic molecules. Our algorithm extends the symmetry driven structure search method [Phys. Rev. B 98 (2018) 174107] by adding constraints for the bond length and the number of atoms in a molecule, while still maintaining generality. As a method of validation, we have tested our approach for dense hydrogen and reproduced the known molecular structures of Cmca-12 and Cmca-4. We apply our algorithm to study chlorine and fluorine in the pressure range from 10--4000 GPa while considering crystal structures with up to 40 atoms per unit cell. We predict chlorine to follow the same series of phase transformations as elemental iodine from Cmca to Immm to Fm$\bar{3}$m, but at substantially higher pressures. We predict fluorine to transition from a C2/c to an Cmca structure at 70 GPa, to a novel orthorhombic and metallic structure with P$4_2$/mmc symmetry at 2500 GPa, and finally into its cubic analogue form with Pm$\bar{3}$n symmetry at 3000 GPa.