Structural studies of pressure-induced phase transitions in selenium up to 150 GPa

Akahama, Yuichi; Kobayashi, Masakazu; Kawamura, Haruki

doi:10.1103/physrevb.47.20

Cited by 121 publications

(107 citation statements)

References 14 publications

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“…[2][3][4][5][6] In comparison with this case of t-Se, the structures of the high pressure phases of r-Se, 7) o-Se, 8) and m-Se 9) have been unclear because of the following two reasons. One is that the high pressure behavior in these allotropes was investigated before the determination of the structures of Se-III, Se-IV, and Se-II' (tetragonal form consisting of 4 1 and 4 3 helical chain molecules) which is one of the high pressure phases of m-Se, 10) and the other is that the high pressure phases at pressure between 10 GPa and 30 GPa are mixture phases and that the diffraction patterns of these phases are complex.…”

Section: Introductionmentioning

confidence: 91%

“…Selenium (Se) has several crystalline allotropes; namely trigonal (t-Se or Se-I), rhombohedral (r-Se), orthorhombic (o-Se), and -monoclinic (m-Se) modifications, which consist of 3 1 helical chain, Se 6 , Se 7 , and Se 8 ring molecules, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4][5][6][7][8][9][10] The generally accepted transition sequence in t-Se is Se-I to Se-II (monoclinic form, puckered layer structure) at 14 GPa, Se-II to Se-III (triclinic form) at 23 GPa, Se-III to Se-IV (incommensurate monoclinic form) at 28 GPa, Se-IV to Se-V ( -Po structure) at 80 GPa, and Se-V to Se-VI (bcc) at 140 GPa. [2][3][4][5][6] In comparison with this case of t-Se, the structures of the high pressure phases of r-Se, 7) o-Se, 8) and m-Se 9) have been unclear because of the following two reasons. One is that the high pressure behavior in these allotropes was investigated before the determination of the structures of Se-III, Se-IV, and Se-II' (tetragonal form consisting of 4 1 and 4 3 helical chain molecules) which is one of the high pressure phases of m-Se, 10) and the other is that the high pressure phases at pressure between 10 GPa and 30 GPa are mixture phases and that the diffraction patterns of these phases are complex.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Pressure-Induced Phase Transitions of Trigonal, Rhombohedral, Orthorhombic, and α-Monoclinic Selenium

Takumi

Nagata

2007

J. Phys. Soc. Jpn.

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Pressure-induced phase transitions of trigonal, rhombohedral, orthorhombic, and -monoclinic selenium (Se), which consist of 3 1 helical chain, Se 6 , Se 7 , and Se 8 ring molecules, respectively, have been re-examined by an X-ray diffraction method. All allotropes transform to Se-IV (incommensurate monoclinic form) at about 30 GPa through a mixture phase of Se-II (monoclinic form, puckered layer structure) and Se-II' (tetragonal form consisting of 4 1 and 4 3 helical chain molecules). The ratio of Se-II to Se-II' in the mixture phase increases with the increase in density of starting material.Trigonal form (Se-I) transforms to Se-I', which is isostructural with Se-I, at 3 GPa, where an intramolecular covalent bond length decreases abruptly by about 0.8 %.KEYWORDS: selenium, allotropes, phase diagram, high pressure, x-ray diffraction IntroductionSelenium (Se) has several crystalline allotropes; namely trigonal (t-Se or Se-I), rhombohedral (r-Se), orthorhombic (o-Se), and -monoclinic (m-Se) modifications, which consist of 3 1 helical chain, Se 6 , Se 7 , and Se 8 ring molecules, respectively.1) The pressure-induced phase transitions of these allotropes have been investigated.2-10) The generally accepted transition sequence in t-Se is Se-I to Se-II (monoclinic form, puckered layer structure) at 14 GPa, Se-II to Se-III (triclinic form) at 23 GPa, Se-III to Se-IV (incommensurate monoclinic form) at 28 GPa, Se-IV to Se-V ( -Po structure) at 80 GPa, and Se-V to Se-VI (bcc) at 140 GPa. [2][3][4][5][6] In comparison with this case of t-Se, the structures of the high pressure phases of r-Se, 7) o-Se, 8) and m-Se 9) have been unclear because of the following two reasons. One is that the high pressure behavior in these allotropes was investigated before the determination of the structures of Se-III, Se-IV, and Se-II' (tetragonal form consisting of 4 1 and 4 3 helical chain molecules) which is one of the high pressure phases of m-Se, 10) and the other is that the high pressure phases at pressure between 10 GPa and 30 GPa are mixture phases and that the diffraction patterns of these phases are complex. In this paper, in order to clarify the phase diagrams of selenium allotropes, we have re-examined the phase transitions of four kinds of selenium allotropes, t-Se, r-Se, o-Se, and m-Se using an X-ray diffraction method.

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Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Pressure-Induced Phase Transitions of Trigonal, Rhombohedral, Orthorhombic, and α-Monoclinic Selenium

Takumi

Nagata

2007

J. Phys. Soc. Jpn.

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“…Under pressure, selenium exhibits a complex polymorphism, and the diversity of phases and transition sequences observed depend strongly on the starting material (12,(14)(15)(16)(17)(18)(19)(20)(21). First studied by x-ray diffraction (XRD) in 1972 (22), a-Se was found to crystallize in a trigonal structure (t-Se) at Ϸ10 GPa (23-27).…”

mentioning

confidence: 99%

Anomalous high-pressure behavior of amorphous selenium from synchrotron x-ray diffraction and microtomography

Liu

Wang

Xiao

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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The high-pressure behavior of amorphous selenium has been investigated with time-resolved diamond anvil cell synchrotron x-ray diffraction and computed microtomography techniques. A two-step dynamic crystallization process is observed in which the monoclinic phase crystallized from the amorphous selenium and gradually converted to the trigonal phase, thereby explaining previously observed anomalous changes in electrical conductivity of the material under pressure. The crystallization of this elemental system involves local topological fluctuations and results in an unusual pressure-induced volume expansion. The metastability of the phases involved in the transition accounts for this phenomenon. The results demonstrate the use of pressure to control and directly monitor the relative densities and energetics of phases to create new phases from highly metastable states. The microtomographic technique developed here represents a method for determination of the equations of state of amorphous materials at extreme pressures and temperatures.crystallization ͉ volume expansion ͉ equation of state ͉ phase transition ͉ metastability T he behavior of amorphous materials under pressure is a problem of great current interest. Unusual behavior, such as pressure-induced amorphization of crystalline forms, pressureinduced polyamorphism low-to high-density forms of insulating and metallic glasses, and the dynamics of pressure-induced crystallization are reported but not fully understood (1-10). The nature of the behavior of amorphous solids under pressure is complicated by their metastability and the possibility of irreversible relaxation of their properties and structure (11). Amorphous selenium (a-Se) is a model system for examining pressure effects in amorphous materials because of the wide range of structure and bonding properties expected based on the behavior of the crystalline polymorphs of the element. In experiments designed to understand the high-pressure behavior of a-Se, we have discovered an unexpected pressure-induced dynamic crystallization process associated with a volume expansion in the material. The origin of this unusual phenomenon is examined by using a microtomography technique that allows direct measurement of the equation of state (EOS) of the amorphous phase.Recent efforts to characterize the structural evolution of group VI elements under pressure, such as novel dense chain structures in sulfur and selenium (12), and the alternating phase transition sequence in sulfur at high pressure and temperature (13), have led to a new level of understanding of the phase diagrams and structures of these materials. Under pressure, selenium exhibits a complex polymorphism, and the diversity of phases and transition sequences observed depend strongly on the starting material (12,(14)(15)(16)(17)(18)(19)(20)(21). First studied by x-ray diffraction (XRD) in 1972 (22), a-Se was found to crystallize in a trigonal structure (t-Se) at Ϸ10 GPa (23-27). However, its electrical resistance was clearly different from pure t-Se i...

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“…Generally, there is a constant increase of CN upon changing from low-coordinated semiconductors -sulphur and selenium showing a large variety of allotropes already at ambient pressure -with highly anisotropic (heterodesmic) bonding towards 3D-connected solid state arrangements [88][89][90][91][92][93][94][95][96][97][98][99][100], e.g., that of non-centrosymmetric Te-II (Fig. 13).…”

Section: Chalcogens Halogens and Noble Gasesmentioning

confidence: 99%

Metallic high-pressure modifications of main group elements

Schwarz¹

2004

Zeitschrift Für Kristallographie - Crystalline Materials

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Abstract. The high-pressure structural chemistry of main group elements in the metallic state is reviewed under consideration of more recent determinations of atomic arrangements with to some extend unexpected complexity. Following the concept of the pressure-coordination rule, the number of nearest neighbours is employed as a guiding quantity to reveal systematic trends. Violations of the rule will be mainly discussed in the light of electronic ground state changes upon compression.

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Structural studies of pressure-induced phase transitions in selenium up to 150 GPa

Cited by 121 publications

References 14 publications

Pressure-Induced Phase Transitions of Trigonal, Rhombohedral, Orthorhombic, and α-Monoclinic Selenium

Pressure-Induced Phase Transitions of Trigonal, Rhombohedral, Orthorhombic, and α-Monoclinic Selenium

Anomalous high-pressure behavior of amorphous selenium from synchrotron x-ray diffraction and microtomography

Metallic high-pressure modifications of main group elements

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