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Lundegaard LF, McMahon MI. Single crystal studies of pure elements at high pressure. Acta Crystallogr A 2007. [DOI: 10.1107/s0108767307098765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Loa I, Lundegaard LF, McMahon MI, Evans SR, Bossak A, Krisch M. Lattice dynamics of incommensurate composite Rb-IV and a realization of the monatomic linear chain model. PHYSICAL REVIEW LETTERS 2007; 99:035501. [PMID: 17678293 DOI: 10.1103/physrevlett.99.035501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Indexed: 05/16/2023]
Abstract
Longitudinal-acoustic (LA) phonons have been studied by inelastic x-ray scattering in the high-pressure incommensurate host-guest system Rb-IV in the pressure range of 16.3 to 18.4 GPa. Two LA-like phonon branches are observed along the direction of the incommensurate wave vector, which are attributed to separate lattice vibrations in the host and guest subsystems. The derived sound velocities for the host and the guest, v(h) and v(g), respectively, are similar in magnitude [v(h)=v(g)=3840(100) m/s at 18 GPa], but our results indicate rather different pressure dependences of dv(h)/dP=140(60) m/s GPa(-1) and dv(g)/dP=280(80) m/s GPa(-1). The observations for the one-dimensional Rb guest chains are reproduced quantitatively on the basis of the monatomic linear chain model and the measured compressibility of the chains.
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McMahon MI, Nelmes RJ. Observation of a wurtzite form of gallium arsenide. PHYSICAL REVIEW LETTERS 2005; 95:215505. [PMID: 16384157 DOI: 10.1103/physrevlett.95.215505] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Indexed: 05/05/2023]
Abstract
After a pressure decrease to ambient, the high-pressure SC16 phase of GaAs is found to transform to the hexagonal wurtzite structure. This has been suggested for GaAs in calculations but never previously observed experimentally. Wurtzite-GaAs is found to be stable at ambient pressures at temperatures up to 473 K, with a structure that is only slightly distorted from ideal. On recompression, the ratio is constant with pressure and wurtzite-GaAs transforms to the orthorhombic phase at 18.7(9) GPa.
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Hejny C, Lundegaard L, Falconi S, McMahon MI. Single crystal studies using the 9.8 station at SRS Daresbury. Acta Crystallogr A 2005. [DOI: 10.1107/s0108767305094365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Rousse G, Klotz S, Saitta AM, Rodriguez-Carvajal J, McMahon MI, Mezouar M, Couzinet B. Resolution of the intermediate high pressure phase of PbTe. Acta Crystallogr A 2005. [DOI: 10.1107/s0108767305080682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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31
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Bovornratanaraks T, Saengsuwan V, Yoodee K, McMahon MI, Hejny C. Structures and phase transitions of CuInSe 2under high pressure. Acta Crystallogr A 2005. [DOI: 10.1107/s0108767305080657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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32
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Falconi S, Lundegaard LF, Hejny C, McMahon MI. X-ray diffraction study of liquid Cs up to 9.8 GPa. PHYSICAL REVIEW LETTERS 2005; 94:125507. [PMID: 15903934 DOI: 10.1103/physrevlett.94.125507] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Indexed: 05/02/2023]
Abstract
We describe an x-ray diffraction study of liquid Cs at high pressure and temperature conducted in order to characterize the structural changes associated with the complex melting curve and phase transitions observed in the solid phases. At 3.9 GPa we observe a discontinuity in the density of the liquid accompanied by a decrease in the coordination number from about 12 to 8, which marks a change to a nonsimple liquid. The specific volume of liquid Cs, combined with structural analysis of the diffraction data, strongly suggest the existence of dsp(3) electronic hybridization above 3.9 GPa, similar to that reported on compression in the crystalline phase.
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Degtyareva O, McMahon MI, Allan DR, Nelmes RJ. Structural complexity in gallium under high pressure: relation to alkali elements. PHYSICAL REVIEW LETTERS 2004; 93:205502. [PMID: 15600936 DOI: 10.1103/physrevlett.93.205502] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2004] [Indexed: 05/24/2023]
Abstract
Ga-II, the stable phase of Ga between 2 and 10 GPa at room temperature, is shown to have a complex 104-atom orthorhombic structure. A new phase, Ga-V, is found between 10 and 14 GPa, with a rhombohedral hR6 structure. Ga-II has a modulated layer structure like those recently reported for Rb-III and Cs-III, with similar 8- and 10-atom a-b layers stacked along the c axis in the sequence 8-10-8-8-10-8-8-10-8-8-10-8. The cI16 structure of Li and Na can be understood as a stacking of very similar 8-atom layers. It is suggested that a Hume-Rothery mechanism contributes to the occurrence of these complex structures in such different metals.
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McMahon MI. Novel structures in 'simple' metals. Acta Crystallogr A 2004. [DOI: 10.1107/s0108767304099908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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McMahon MI, Nelmes RJ. Chain "melting" in the composite Rb-IV structure. PHYSICAL REVIEW LETTERS 2004; 93:055501. [PMID: 15323704 DOI: 10.1103/physrevlett.93.055501] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Indexed: 05/24/2023]
Abstract
The Bragg peaks from the structure formed by the guest chains in the incommensurate composite structure of Rb-IV are all found to broaden strongly at pressures below 16.7(1) GPa. This signals a loss of the interchain correlation. At the lowest reachable pressure before the transition to Rb-III, 16.2 GPa, the correlation length is only approximately 30 A, or 4 times the interchain distance. There is also evidence of a loss of long-range order within each chain. The chains thus exhibit the onset of the characteristics of an ordered 1D liquid.
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Hejny C, McMahon MI. Large structural modulations in incommensurate Te-III and Se-IV. PHYSICAL REVIEW LETTERS 2003; 91:215502. [PMID: 14683313 DOI: 10.1103/physrevlett.91.215502] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2003] [Indexed: 05/24/2023]
Abstract
The high-pressure phase of tellurium, Te-III, is found to have an incommensurate monoclinic structure, superspace group I(')2/m(0q0)s0, of a type previously unknown in the elements. Te-III is stable from 4.5(2) to 29.2(7) GPa; the previously reported transition to a distinct Te-IV phase at 10.6 GPa is not observed. The incommensurate wave vector of Te-III is strongly pressure dependent and varies in a strongly nonlinear way. Se-IV is found to be isostructural with Te-III.
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Nelmes RJ, McMahon MI, Degtyareva O, Bovornratanaraks T, Hejny C, Rekhi S, Allan DR, Loveday JS, Belmonte SA. Complex metal structures at high pressures. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302092140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Hejny C, McMahon MI, Nelmes RJ. Search for interstitial electrons in the structure of Cs-IV. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302092036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Degtyareva O, McMahon MI, Nelmes RJ. High pressure structural studies on gallium. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302092048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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McMahon MI, Degtyareva O, Nelmes RJ, Palatinus L, van Smaalen S. Incommensurate modulations in the structure of Bi-III. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302092139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Nelmes RJ, McMahon MI, Loveday JS, Rekhi S. Structure of Rb-III: novel modulated stacking structures in alkali metals. PHYSICAL REVIEW LETTERS 2002; 88:155503. [PMID: 11955205 DOI: 10.1103/physrevlett.88.155503] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2002] [Indexed: 05/23/2023]
Abstract
The crystal structure of Rb-III, stable between 13 and 17 GPa, has been determined from quasi-single-crystal x-ray diffraction data. It is orthorhombic, space group C222(1), with 52 atoms in the unit cell, and has an 8-10-8-8-10-8 stacking of 8- and 10-atom layers. The recently reported 84-atom structure of Cs-III can be understood as an 8-8-10-8-8-8-8-10-8-8 stacking of the same layers. These represent a new class of modulated elemental structures.
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McMahon MI, Nelmes RJ, Rekhi S. Complex crystal structure of cesium-III. PHYSICAL REVIEW LETTERS 2001; 87:255502. [PMID: 11736587 DOI: 10.1103/physrevlett.87.255502] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2001] [Indexed: 05/23/2023]
Abstract
The structure of Cs-III, stable between 4.2 and 4.3 GPa at room temperature, has been determined from single-crystal x-ray diffraction data. Rather than the simple fcc structure previously reported [Hall et al., Science 146, 1297 (1964)], the data yield a complex new type of elemental structure which is orthorhombic (space group C222(1)) with 84 atoms in the unit cell. No evidence could be found for the fcc form reported previously, even in a further experiment, conducted under conditions close to those used by Hall et al., which also yielded the 84-atom structure.
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McMahon MI, Rekhi S, Nelmes RJ. Pressure dependent incommensuration in Rb-IV. PHYSICAL REVIEW LETTERS 2001; 87:055501. [PMID: 11497781 DOI: 10.1103/physrevlett.87.055501] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2001] [Indexed: 05/23/2023]
Abstract
Rb-IV is found to have an incommensurate composite structure, comprising a tetragonal host framework and a simple body-centered tetragonal guest. This does not have the unexpectedly short Rb-Rb distances of the previously reported structure [U. Schwarz et al., Phys. Rev. Lett. 83, 4085 (1999)]. The ratio of the c-axis lattice parameters is strongly pressure dependent and approaches the commensurate value of 5/3 at the transition to phase V. A reversible broadening of the guest structure is observed below 16.5(2) GPa.
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McMahon MI, Degtyareva O, Nelmes RJ. Ba-IV-type incommensurate crystal structure in group-V metals. PHYSICAL REVIEW LETTERS 2000; 85:4896-4899. [PMID: 11102145 DOI: 10.1103/physrevlett.85.4896] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2000] [Indexed: 05/23/2023]
Abstract
The long-unknown crystal structure of Bi-III has been solved. It comprises a body-centered-tetragonal (bct) "host" and a bct "guest" component made up of chains that lie in channels in the host; the guest is incommensurate with the host along the tetragonal c axis. Diffraction data for Sb-II reveal that it too can be fitted with the same composite structure. The structures of these two high-pressure phases of Bi and Sb are similar to those reported recently in the alkaline-earth metals Ba and Sr.
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Allan DR, Nelmes RJ, McMahon MI, Belmonte SA, Bovornratanaraks T. Structures and Transitions in Strontium. ACTA ACUST UNITED AC 1998. [DOI: 10.4131/jshpreview.7.236] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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McMahon MI, Nelmes RJ, Liu H, Belmonte SA. "Hidden" High-to-Low Cristobalite Type Transition in HgSe and HgTe at High Pressure. PHYSICAL REVIEW LETTERS 1996; 77:1781-1784. [PMID: 10063170 DOI: 10.1103/physrevlett.77.1781] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Belmonte SA, Nelmes RJ, McMahon MI. 2-D analysis of non-ideal powders using an image-plate detector. Acta Crystallogr A 1996. [DOI: 10.1107/s010876739607780x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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48
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McMahon MI, Nelmes RJ. High-pressure structural studies of lanthanides. Acta Crystallogr A 1996. [DOI: 10.1107/s0108767396078464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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49
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Nelmes RJ, McMahon MI, Liu H, Belmonte SA. New structural systematics in the II–VI, III–V and group IV semiconductors at high pressure. Acta Crystallogr A 1996. [DOI: 10.1107/s0108767396078397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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50
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Nelmes RJ, McMahon MI. Identity of InSb-II and InSb-III. PHYSICAL REVIEW LETTERS 1996; 77:663-666. [PMID: 10062871 DOI: 10.1103/physrevlett.77.663] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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