CaCl2-type high-pressure phase of magnesium hydride predicted byab initiophonon calculations

A pressure-induced transition in magnesium hydride $(\mathrm{Mg}{\mathrm{H}}_{2})$ from the tetragonal rutile phase to an orthorhombic $\mathrm{Ca}{\mathrm{Cl}}_{2}$ phase is predicted by ab initio phonon calculations. The phase transition is identified as a second-order nature, driven by the softening of the Raman active ${B}_{1g}$ phonon mode, weakly coupling with the elastic shear modulus ${C}_{s}$. The newly predicted $\mathrm{Ca}{\mathrm{Cl}}_{2}$ phase is dynamically stable, and the calculated equation of states shows good agreement with the available experimental data. Analysis of the calculated results of Gibbs free energies and Raman active phonons for both rutile and $\mathrm{Ca}{\mathrm{Cl}}_{2}$ phase, and the spontaneous strains for $\mathrm{Ca}{\mathrm{Cl}}_{2}$ phase, further supports the existence of this new phase.

[1]  Zhengxiao Guo,et al.  Metastable MgH2 phase predicted by first principles calculations , 2006 .

[2]  S. Nakano,et al.  Structural Phase Transition of Rutile-Type MgH2 at High Pressures , 2006 .

[3]  H. Fjellvåg,et al.  Structural stability and pressure-induced phase transitions in MgH 2 , 2006 .

[4]  R. Scalettar,et al.  High Pressure Structure of Half-Metallic CrO2 , 2006 .

[5]  D. Lampakis,et al.  High-pressure Raman study of the ferroelastic rutile-to-CaCl2phase transition inZnF2 , 2005 .

[6]  M. Stachiotti,et al.  Shell-model description of lattice dynamical properties of MgH2 , 2005 .

[7]  L. Hector,et al.  Energetics of the Li amide/Li imide hydrogen storage reaction , 2005 .

[8]  G. D. Price,et al.  Ab initio theory of planetary materials , 2005 .

[9]  M. Gillan,et al.  Structural stability of silica at high pressures and temperatures , 2005 .

[10]  H. Mao,et al.  Brillouin and Raman spectroscopy of the ferroelastic rutile-to-CaCl2 transition in SnO2 at high pressure , 2003 .

[11]  Matt Probert,et al.  First-principles simulation: ideas, illustrations and the CASTEP code , 2002 .

[12]  Vienna University of Technology,et al.  First-principles study of the ferroelastic phase transition in CaCl 2 , 2001, cond-mat/0110466.

[13]  Zhi-Qiang Li,et al.  X-ray diffraction and theoretical studies of the high-pressure structures and phase transitions in magnesium fluoride , 2001 .

[14]  J. Hafner,et al.  Ab initio studies of high-pressure transformations in Ge O2 , 2001 .

[15]  Stefano de Gironcoli,et al.  Phonons and related crystal properties from density-functional perturbation theory , 2000, cond-mat/0012092.

[16]  H. A. Peretti,et al.  Vibrational spectrum of magnesium hydride , 2000 .

[17]  K. Yvon,et al.  Structure of the high pressure phase γ-MgH2 by neutron powder diffraction , 1999 .

[18]  A. Zunger,et al.  Theory of Systematic Absence of NaCl-Type ( β-Sn-Type) High Pressure Phases in Covalent (Ionic) Semiconductors , 1999 .

[19]  M. Scheffler,et al.  Ab initio pseudopotentials for electronic structure calculations of poly-atomic systems using density-functional theory , 1998, cond-mat/9807418.

[20]  Brendan J. Kennedy,et al.  Structural Studies of Rutile-Type Metal Dioxides , 1997 .

[21]  J. Leger,et al.  X-ray diffraction study of the phase transitions and structural evolution of tin dioxide at high pressure:ffRelationships between structure types and implications for other rutile-type dioxides , 1997 .

[22]  J. Crain,et al.  Ab initio studies of high-pressure structural transformations in silica , 1997 .

[23]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[24]  S. Baroni,et al.  The phonon spectra of LiH and LiD from density-functional perturbation theory , 1996 .

[25]  Kieron Burke,et al.  Comparison shopping for a gradient-corrected density functional , 1996 .

[26]  J. Haines,et al.  Second-order rutile-type to CaCl2-type phase transition in β-MnO2 at high pressure , 1995 .

[27]  Michele Parrinello,et al.  FIRST-PRINCIPLE-CONSTANT PRESSURE MOLECULAR DYNAMICS , 1995 .

[28]  H. Mao,et al.  Transformation of stishovite to a denser phase at lower-mantle pressures , 1995, Nature.

[29]  Haines,et al.  Phase transitions in ruthenium dioxide up to 40 GPa: Mechanism for the rutile-to-fluorite phase transformation and a model for the high-pressure behavior of stishovite SiO2. , 1993, Physical review. B, Condensed matter.

[30]  Baroni,et al.  Phonon softening and high-pressure low-symmetry phases of cesium iodide. , 1992, Physical review letters.

[31]  Scheffler,et al.  Analysis of separable potentials. , 1991, Physical review. B, Condensed matter.

[32]  Stefano de Gironcoli,et al.  Ab initio calculation of phonon dispersions in semiconductors. , 1991, Physical review. B, Condensed matter.

[33]  Martins,et al.  Efficient pseudopotentials for plane-wave calculations. , 1991, Physical review. B, Condensed matter.

[34]  Ruoff,et al.  High-pressure studies of NaH to 54 GPa. , 1987, Physical review. B, Condensed matter.

[35]  Testa,et al.  Green's-function approach to linear response in solids. , 1987, Physical review letters.

[36]  O. H. Nielsen,et al.  Stress theorem in the determination of static equilibrium by the density functional method , 1986 .

[37]  J. Vassiliou.  Pressure dependence of the elastic moduli of single crystal MgF2 to 1 GPa , 1985 .

[38]  H. Monkhorst,et al.  "Special points for Brillouin-zone integrations"—a reply , 1977 .

[39]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

[40]  Peter Pulay,et al.  Ab initio calculation of force constants and equilibrium geometries in polyatomic molecules , 1969 .

[41]  E. Lilley,et al.  COMPRESSIONS OF ISOTOPIC LITHIUM HYDRIDES. , 1968 .

[42]  W. Zachariasen,et al.  NEUTRON DIFFRACTION STUDY OF MAGNESIUM DEUTERIDE , 1963 .

[43]  F. Murnaghan.  The Compressibility of Media under Extreme Pressures. , 1944, Proceedings of the National Academy of Sciences of the United States of America.