Erratum: Theoretical study of the structure of calcium in phases IV and V via<i>ab initio</i>metadynamics simulation [Phys. Rev. B<b>77</b>, 020101(R) (2008)]

Ishikawa, Takahiro; Ichikawa, Ayako; Nagara, Hitose; Geshi, Masaaki; Kusakabe, Kouichi; Suzuki, N.

doi:10.1103/physrevb.78.029901

Cited by 11 publications

(20 citation statements)

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“…Thus, we have performed a series of angle-dispersive powder XRD (AD-XRD) HP-HT experiments using DACs and resistive heating to study Ca up to 50 GPa and 800 K. Here, we present thermal equations of state (EOSs) for Ca-I, Ca-II, and Ca-III, and determine the boundaries between these phases. The results are discussed with reference to the previous information available in the literature [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 98%

“…The Ca-III phase is stable up to 113 GPa, whereupon it transforms into the Ca-IV phase, and then a further transformation into the Ca-V phase takes place above 139 GPa [11]. The space groups of the Ca-IV and Ca-V phases were later clarified as tetragonal P 4 1 2 1 2 and orthorhombic Cmca, respectively [12,13]. Under further compression, the Ca-V phase (Cmca) transforms to the orthorhombic Ca-VI structure (space group Pnma) at 158 GPa [14].…”

Section: Introductionmentioning

confidence: 99%

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Phase diagram of calcium at high pressure and high temperature

Anzellini

Errandonea

MacLeod

et al. 2018

Phys. Rev. Materials

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Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murnaghan equation of state with a Berman-type thermal expansion model.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Phase diagram of calcium at high pressure and high temperature

Anzellini

Errandonea

MacLeod

et al. 2018

Phys. Rev. Materials

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“…Actually several other structures including Pnma, Cmca and P4 3 2 1 2 were proposed for the high pressure Ca-IV and Ca-V phases. 23,24,25,26 Their structural details are listed in Table I and their structures are pictured in reference [23,24,25]. I43m is a body-centered cubic structure, Pnma and Cmca Ca are orthorhombic, and P4 3 2 1 2 has a tetragonal symmetry.…”

Section: Theoretical Approach a Competing Structuresmentioning

confidence: 99%

“…So far the higher pressure phases Ca-IV and Ca-V have attracted the most attention, and considerable progress has been made in identifying these phases through a combination of experimental 9,22,23 and theoretical 24,25,26 work. However, satisfactory agreement between experimental and theoretical work is still lacking.…”

Section: Comparison To Related Metalsmentioning

confidence: 99%

Competing phases, strong electron-phonon interaction, and superconductivity in elemental calcium under high pressure

Gygi

Pickett

2009

Phys. Rev. B

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The observed "simple cubic" (sc) phase of elemental Ca at room temperature in the 32-109 GPa range is, from linear response calculations, dynamically unstable. By comparing first principle calculations of the enthalpy for five sc-related (non-close-packed) structures, we find that all five structures compete energetically at room temperature in the 40-90 GPa range, and three do so in the 100-130 GPa range. Some competing structures below 90 GPa are dynamically stable, i.e., no imaginary frequency, suggesting that these sc-derived short-range-order local structures exist locally and can account for the observed (average) "sc" diffraction pattern. In the dynamically stable phases below 90 GPa, some low frequency phonon modes are present, contributing to strong electron-phonon (EP) coupling as well as arising from the strong coupling. Linear response calculations for two of the structures over 120 GPa lead to critical temperatures in the 20-25 K range as is observed, and do so without unusually soft modes.

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“…In fact, the pressures of pure calcium estimated by the generalized gradient approximation calculation, which is the same method as the present one, are much lower than those of experimental values. 19 We expect that the AlB 2 structure will be observed at higher pressures in the experiment.…”

Section: Results Of the Calculations A Optimizations Of The Strmentioning

confidence: 99%

Theoretical Evidences for Enhanced Superconducting Transition Temperature of CaSi₂ in a High-Pressure AlB₂ Phase

et al. 2008

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By means of first-principles calculations, we studied stable lattice structures and estimated superconducting transition temperature of CaSi2 at high pressure. Our simulation showed stability of the AlB2 structure in a pressure range above 17 GPa. In this structure, doubly degenerated optical phonon modes, in which the neighboring silicon atoms oscillate alternately in a silicon plane, show prominently strong interaction with the conduction electrons. In addition there exists a softened optical mode (out-of-plan motion of silicon atoms), whose strength of the electron-phonon interaction is nearly the same as the above mode. The density of states at the Fermi level in the AlB2 structure is higher than that in the trigonal structure. These findings and the estimation of the transition temperature strongly suggest that higher Tc is expected in the AlB2 structure than the trigonal structures which are known so far.

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Erratum: Theoretical study of the structure of calcium in phases IV and V viaab initiometadynamics simulation [Phys. Rev. B77, 020101(R) (2008)]

Cited by 11 publications

References 0 publications

Phase diagram of calcium at high pressure and high temperature

Phase diagram of calcium at high pressure and high temperature

Competing phases, strong electron-phonon interaction, and superconductivity in elemental calcium under high pressure

Theoretical Evidences for Enhanced Superconducting Transition Temperature of CaSi₂ in a High-Pressure AlB₂ Phase

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Erratum: Theoretical study of the structure of calcium in phases IV and V viaab initiometadynamics simulation [Phys. Rev. B77, 020101(R) (2008)]

Cited by 11 publications

References 0 publications

Phase diagram of calcium at high pressure and high temperature

Phase diagram of calcium at high pressure and high temperature

Competing phases, strong electron-phonon interaction, and superconductivity in elemental calcium under high pressure

Theoretical Evidences for Enhanced Superconducting Transition Temperature of CaSi2 in a High-Pressure AlB2 Phase

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Theoretical Evidences for Enhanced Superconducting Transition Temperature of CaSi₂ in a High-Pressure AlB₂ Phase