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Journal Articles

$$P$$-$$T$$ phase diagram and structural transformations of molten P$$_{2}$$O$$_{5}$$ under pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Lyapin, A. G.*; Saito, Hiroyuki

Physical Review B, 89(10), p.104203_1 - 104203_4, 2014/03

 Times Cited Count:7 Percentile:34.91(Materials Science, Multidisciplinary)

The P$$_{2}$$O$$_{5}$$ compound is an archetypical glass-forming oxide. We present the in situ X-ray diffraction study of the pressure-temperature phase diagram of P$$_{2}$$O$$_{5}$$ and of the liquid P$$_{2}$$O$$_{5}$$ structure under high pressure up to 10 GPa. We found that structural transformation in the liquid P$$_{2}$$O$$_{5}$$ under pressure is unique and includes three stages: first, the disappearance of the intermediate range order of the melt together with a slow increase in the average first-coordination number $$<$$$$N$$$$_{1}$$$$>$$ (P-O and O-P neighbors) up to 4 GPa; second, the "normal" compression almost without structural modification at higher pressures up to 8-9 GPa; and, finally, the abrupt change of the short-range order structure of the liquid with the jumplike $$<$$$$N$$$$_{1}$$$$>$$ increase at 9-10 GPa.

Journal Articles

Pressure-driven liquid-liquid transformations and corresponding bizarre viscosity behavior

Brazhkin, V. V.*; Katayama, Yoshinori; Kanzaki, Masami*; Lyapin, A. G.*

Advances in Chemical Physics, Vol.152, p.29 - 50, 2013/04

In recent years, transformations in the melts of elementary substances and oxides have been found under high pressure. These transformations are accompanied by structural changes and variations in physical properties. In this work, structure and viscosity of Se, AsS, AsS, As$$_{2}$$S$$_{3}$$ and B$$_{2}$$O$$_{3}$$ were studied using synchrotron radiation. These substances exhibit changes in bonding in the crystalline state under high pressure. An X-ray diffraction measurements and falling sphere viscosity measurements using an X-ray radiography technique were carried out. Huge change in viscosity which accompanies structural change under compression was observed in each substance.

Journal Articles

Energy-dispersive X-ray diffraction study of liquid gallium under high pressure at elevated temperatures

Yagafarov, O.; Katayama, Yoshinori; Brazhkin, V. V.*; Lyapin, A. G.*; Saito, Hiroyuki

High Pressure Research, 33(1), p.191 - 195, 2013/01

 Times Cited Count:5 Percentile:41.28(Physics, Multidisciplinary)

Journal Articles

Energy dispersive X-ray diffraction and reverse Monte Carlo structural study of liquid gallium under pressure

Yagafarov, O.; Katayama, Yoshinori; Brazhkin, V. V.*; Lyapin, A. G.*; Saito, Hiroyuki

Physical Review B, 86(17), p.174103_1 - 174103_9, 2012/11

 Times Cited Count:26 Percentile:73.33(Materials Science, Multidisciplinary)

Journal Articles

Pressure-induced structural transformations and the anomalous behavior of the viscosity in network chalcogenide and oxide melts

Brazhkin, V. V.*; Katayama, Yoshinori; Kanzaki, Masami*; Kondrin, M. V.*; Lyapin, A. G.*

JETP Letters, 94(2), p.161 - 170, 2011/09

 Times Cited Count:11 Percentile:60.12(Physics, Multidisciplinary)

It is known that a number of compressed melts undergo structural phase transitions. Data on the structural changes at high pressures in chalcogenides (AsS, As$$_{2}$$S$$_{3}$$) and oxide (B$$_{2}$$O$$_{3}$$) melts with a network structure have been reviewed. Viscosity is one of the fundamental physical properties of a liquid. For various melts, it varies in a very wide range. Structural transformations in melts induce the corresponding changes in all physical properties, in particular viscosity. The measurements of the viscosity of a number of melts at high pressures and temperatures by the radiographic method have been reported. Changes in the viscosity by several orders of magnitude have been detected when the pressure is varied by several gigapascals. The diffusion mechanism in network structure melts at various pressures has been analyzed.

Journal Articles

Densified low-hygroscopic form of P$$_{2}$$O$$_{5}$$ glass

Brazhkin, V. V.*; Akola, J.*; Katayama, Yoshinori; Kohara, Shinji*; Kondrin, M. V.*; Lyapin, A. G.*; Lyapin, S. G.*; Tricot, G.*; Yagafarov, O.

Journal of Materials Chemistry, 21(28), p.10442 - 10447, 2011/07

 Times Cited Count:14 Percentile:44.78(Chemistry, Physical)

P$$_{2}$$O$$_{5}$$ compound is an archetypical glass-forming oxide with a high hygroscopicity. We found that the quenching from the P$$_{2}$$O$$_{5}$$melt under ultrahigh pressures enables obtaining densified P$$_{2}$$O$$_{5}$$ glasses with a residual densification up to 12% at normal conditions. These glasses have a low hygroscopicity and can exist under air conditions for several weeks. An examination of the structure of the new form of P$$_{2}$$O$$_{5}$$ glass reveals a cardinal decrease of the volume of nanovoids in the glassy matrix.

Journal Articles

Structural transformation yielding an unusual metallic state in liquid As$$_{2}$$S$$_{3}$$ under high pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Kondrin, M. V.*; Lyapin, A. G.*; Saito, Hiroyuki

Physical Review B, 82(14), p.140202_1 - 140202_4, 2010/10

 Times Cited Count:14 Percentile:54.85(Materials Science, Multidisciplinary)

The As$$_{2}$$S$$_{3}$$ melt at room pressure represents a liquid having a three-dimensional network structure, semiconducting properties, and a huge viscosity. We have found that under high pressure a considerable change in the medium and short-range structure of this liquid is observed. Intermediate-range order correlations in the atomic arrangement almost disappear under pressure and an increase in the coordination number is observed.

Journal Articles

Structural transformations and anomalous viscosity in the B$$_{2}$$O$$_{3}$$ melt under high pressure

Brazhkin, V. V.*; Farnan, I.*; Funakoshi, Kenichi*; Kanzaki, Masami*; Katayama, Yoshinori; Lyapin, A. G.*; Saito, Hiroyuki

Physical Review Letters, 105(11), p.115701_1 - 115701_4, 2010/09

 Times Cited Count:47 Percentile:86.71(Physics, Multidisciplinary)

Liquid B$$_{2}$$O$$_{3}$$ represents an archetypical oxide melt with the cation coordination number 3 and unusual structural units - planar boroxol rings. It features super-high viscosity at melting temperature. The results of the ${it in-situ}$ X-ray diffraction study and ${it in-situ}$ viscosity measurements of the B$$_{2}$$O$$_{3}$$ liquid under high pressure up to 8 GPa are presented. Additionally, the NMR study of B$$_{2}$$O$$_{3}$$ glasses quenched from the melt at different pressures has been carried out. The number of the boroxol rings in the melt rapidly decreases with pressure. The viscosity of the B$$_{2}$$O$$_{3}$$ melt along the melting curve drops by 4 orders of magnitude as the pressure increases up to 5.5 GPa and remains unchanged on further pressure increase.

Journal Articles

Compressibility and polymorphism of $$alpha$$-As$$_{4}$$S$$_{4}$$ realgar under high pressure

Tuktabiev, M. A.*; Popova, S. V.*; Brazhkin, V. V.*; Lyapin, A. G.*; Katayama, Yoshinori

Journal of Physics; Condensed Matter, 21(38), p.385401_1 - 385401_7, 2009/08

 Times Cited Count:15 Percentile:55.92(Physics, Condensed Matter)

The energy-dispersive X-ray diffraction technique has been employed to study the structure and equation of state of realgar As$$_{4}$$S$$_{4}$$ under pressures up to 8 GPa at room temperature. We have obtained pressure dependences of the unit cell parameters and volume for the monoclinic structure of realgar. At a pressure of around 7 GPa, realgar showed a polymorph transition to a new molecular phase with a supposedly orthorhombic structure. The phase transition is likely to be associated with the removal of a monoclinic distortion in the unit cell.

Journal Articles

Investigation of polyamorphism in compressed B$$_{2}$$O$$_{3}$$ glass by the direct measurement of the density

Brazhkin, V. V.*; Tsiok, O. B.*; Katayama, Yoshinori

JETP Letters, 89(5), p.244 - 248, 2009/05

 Times Cited Count:13 Percentile:62.4(Physics, Multidisciplinary)

Relative volume change of vitreous B$$_{2}$$O$$_{3}$$ have been precisely measured by the strain-gauge technique at hydrostatic pressures up to 9 GPa. Smeared anomalies of compressibility (at P $$>$$ 0.5 GPa and P $$>$$ 5 GPa) and logarithmic relaxation of the glass density are observed. It has been revealed that there is a significant difference between the relaxed bulk modulus of glass obtained from the volume measurements and the unrelaxed modulus estimated from the Brillouin spectroscopic data. The basic features of the phase transitions in B$$_{2}$$O$$_{3}$$ glass is revealed by the measurements of the relative volume change under compression together with the previous structure investigations and computer simulation results. Both direct and reverse transitions are smeared in pressure. The residual densification in glass is not associated with change in the short-range order.

Journal Articles

Viscosity behavior spanning four orders of magnitude in As-S melts under high pressure

Brazhkin, V. V.*; Kanzaki, Masami*; Funakoshi, Kenichi*; Katayama, Yoshinori

Physical Review Letters, 102(11), p.115901_1 - 115901_4, 2009/03

 Times Cited Count:18 Percentile:70.95(Physics, Multidisciplinary)

As-S liquid undergoes structural transformation form a molecular liquid into a polymerized one, then into a metallic one. We have measured the viscosity of the As-S liquid under high pressures and found large viscosity variations by 4-5 orders of magnitude. The viscosity values of the As-s liquids are moderate in the molecular state, very high in the covalent state, and low in the metallic state. From these results, it is possible to predict the viscosity behavior in other melts under pressure. The possibility of varying the viscosity value of the melts under pressure by many orders of magnitude is of great importance for materials science and earth science.

Journal Articles

Nature of the structural transformations in B$$_{2}$$O$$_{3}$$ glass under high pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Trachenko, K.*; Tsiok, O. B.*; Lyapin, A. G.*; Artacho, E.*; Dove, M.*; Ferlat, G.*; Inamura, Yasuhiro; Saito, Hiroyuki

Physical Review Letters, 101(3), p.035702_1 - 035702_4, 2008/07

 Times Cited Count:65 Percentile:89.67(Physics, Multidisciplinary)

We study polyamorphism of B$$_{2}$$O$$_{3}$$ glass using X-ray diffraction up to 10 GPa in the 300-700 K temperature range, in situ volumetric measurements up to 9 GPa, and first-principles simulations. The glass undergoes two-stage transformations under pressure including a gradual increase of the first B-O (O-B) coordination numbers above 5 GPa. The fraction of boron atoms in the fourfold-coordinated state at P$$<$$10 GPa is smaller than was assumed from inelastic X-ray scattering spectroscopy data, but is considerably larger than was previously suggested by the classical molecular dynamics simulations. The observed transformations under both compression and decompression are broad in hydrostatic conditions.

Journal Articles

AsS melt under pressure; One substance, three liquids

Brazhkin, V. V.*; Katayama, Yoshinori; Kondrin, M. V.*; Hattori, Takanori; Lyapin, A. G.*; Saito, Hiroyuki

Physical Review Letters, 100(14), p.145701_1 - 145701_4, 2008/04

 Times Cited Count:41 Percentile:83.86(Physics, Multidisciplinary)

An ${it in situ}$ high-temperature high-pressure X-ray diffraction, resistivity measurements, and quenching from melt were performed on liquid chalcogenide AsS. The obtained data provide direct evidence for the existence three forms in the melt under compression: one is a moderate viscosity molecular liquid, the second one is a high-viscosity nonmetallic polymerized liquid and the third one is a low-viscosity metallic liquid. The two transformations occur at P $$sim$$ 1.6-2.2 GPa and at P $$sim$$ 4.6-4.8 GPa. Upon rapid cooling, molecular and metallic liquids crystallize to normal and high-pressure phases, respectively, while a polymerized liquid is easily quenched to a new AsS glass. General aspects of multiple phase transitions in liquid AsS, including relations to the phase diagram of the respective crystalline, are discussed.

Journal Articles

Nonviscous metallic liquid Se

Brazhkin, V. V.*; Funakoshi, Kenichi*; Kanzaki, Masami*; Katayama, Yoshinori

Physical Review Letters, 99(24), p.245901_1 - 245901_4, 2007/12

 Times Cited Count:20 Percentile:69.13(Physics, Multidisciplinary)

Viscosity is one of the fundamental physical properties of liquids; for different melts it varies in an extremely wide range. Selenium is among the first elementary substances to have manifested, at compression, a phase transformation in the liquid state accompanied by melt metallization. Direct measurements by means of a real-time radiography show that the viscosity of liquid Se under pressure drops by 500 times to a very low level of 8 mPa s. This is the first case of viscosity measurements being performed both for a relatively viscous semiconducting state and a low-viscous metallic state of the same liquid substance. The viscosity of the Se melt strongly decreases with pressure along the melting curve in a semiconducting state and experiences a further significant drop at melt metallization. A similar phenomenon is expected to be observed in many chalcohenide, halogenide and oxide melts.

Journal Articles

AsS: Bulk inorganic molecular-based chalcogenide glass

Brazhkin, V. V.*; Gavrilyuk, A. G.*; Lyapin, A. G.*; Timofeev, Yu. A.*; Katayama, Yoshinori; Kohara, Shinji*

Applied Physics Letters, 91(3), p.031912_1 - 031912_3, 2007/07

 Times Cited Count:19 Percentile:59.84(Physics, Applied)

A high pressure method to produce bulk chalcogenide glasses of a unique AsS composition has been developed. The structure, optical properties, and stability of the obtained glasses have been studied. Glasses have an intrinsic deep-red color, opticalpseudogap Eg$$approx$$1.75 eV, a broad Urbach absorption tail W$$_{U}$$$$approx$$120 meV, and high temperature stability up to 130$$^{circ}$$C. AsS glasses show photoinduced transformations, including photocrystallization. The glass structure is largely based on the quasimolecular As$$_{4}$$S$$_{4}$$ units with partial polymerization providing an example of an inorganic molecular-based glass.

Journal Articles

Molecular-network-ionic structure transitions in liquid AlCl$$_{3}$$ and ZnCl$$_{2}$$ halogenides under pressure

Brazhkin, V. V.*; Lyapin, A. G.*; Popova, S. V.*; Katayama, Yoshinori; Saito, Hiroyuki; Utsumi, Wataru

Journal of Physics; Condensed Matter, 19(24), p.246104_1 - 246104_10, 2007/06

 Times Cited Count:22 Percentile:67.42(Physics, Condensed Matter)

Liquid AlCl$$_{3}$$ and ZnCl$$_{2}$$ halogenides are studied by ${it in-situ}$ high-pressure high-temperature X-ray diffraction measurements. These halogenides have a quasi-molecular network structure in liquid state at normal pressure. They are intermediate between pure covalent and ionic melts. The present study is indicative of a rapid and strong breakdown of an intermediate range order in a tetrahedral network of melts for the initial pressure range and points to rather sharp transitions in liquids with the formation of a short-range order structure similar to ionic melt structures. Such a two-stage structural transformation under pressure is the general feature for a wide class of simple melts, including most of the pseudo-covalent halogenides.

Journal Articles

Lattice parameters and thermal expansion of superconducting boron-doped diamonds

Brazhkin, V. V.*; Ekimov, E. A.*; Lyapin, A. G.*; Popova, S. V.*; Rakhmanina, A. V.*; Stishov, S. M.*; Lebedev, V. M.*; Katayama, Yoshinori; Kato, Kenichi*

Physical Review B, 74(14), p.140502_1 - 140502_4, 2006/10

 Times Cited Count:45 Percentile:84.47(Materials Science, Multidisciplinary)

Using two different high-pressure techniques, we have prepared boron-doped diamonds with atomic concentration of the dopant ranging from 0.04% to 4% (from 7$$times$$10$$^{19}$$ to 7$$times$$10$$^{21}$$ atom/cm$$^{3}$$) and studied the lattice constants and thermal expansion of the diamonds in the temperature range from 90 to 300 K. Both sets of samples demonstrate the same increasing concentration dependence of the lattice parameter with maximum shift of the lattice constant about 0.011${AA}$. We have established an abnormally high thermal expansion of the heavily boron-doped superconducting diamonds with respect to the undoped ones and a nearly linear correlation between lattice constant and critical temperature of the superconducting transition.

Journal Articles

Structural studies of phase transitions in crystalline and liquid Halides (ZnCl$$_{2}$$, AlCl$$_{3}$$) under pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Lyapin, A. G.*; Popova, S. V.*; Inamura, Yasuhiro*; Saito, Hiroyuki; Utsumi, Wataru

JETP Letters, 82(11), p.713 - 718, 2005/12

 Times Cited Count:11 Percentile:56.48(Physics, Multidisciplinary)

The results of investigating the phase diagrams of ZnCl$$_{2}$$ and AlCl$$_{3}$$ halides, as well as the structure of the short range order of the corresponding melts under pressures up to 6.5 GPa, by the method of energy-dispersive X-ray diffraction are reported. When a ZnCl$$_{2}$$ crystal is compressed, a phase transition occurs from the $$gamma$$ phase (HgI$$_{2}$$ structure type) to the $$delta$$ phase (distorted CdI$$_{2}$$ structure, WTe$$_{2}$$ type). The structural studies of the liquid state of ZnCl$$_{2}$$ and AlCl$$_{3}$$ indicate that the intermediate-range order decreases rapidly in the tetrahedral network of both melts as the pressure increases to 1.8 and 2.3 GPa for ZnCl$$_{2}$$ and AlCl$$_{3}$$, respectively. With further compression, the transitions in both melts occur with a change in the structure of the short-range order and with an increase in the coordination number. In this case, the transition in AlCl$$_{3}$$ occurs at about 4 GPa and is a sharp first order transition, whereas the transition in ZnCl$$_{2}$$ occurs more smoothly in a pressure range of 2-4 GPa with a maximum intensity near 3 GPa. Thus the AlCl$$_{3}$$ and ZnCl$$_{2}$$ compounds exemplify the existence of two phenomena, gradual decay of intermidiate-range structural correlations and a sharper liquid-liquid coordination transition.

Journal Articles

Structural transformations in liquid, crystalline, and glassy B$$_{2}$$O$$_{3}$$ under high pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Inamura, Yasuhiro; Kondrin, M. V.*; Lyapin, A. G.*; Popova, S. V.*; Voloshin, R. N.*

JETP Letters, 78(6), p.393 - 397, 2003/06

 Times Cited Count:27 Percentile:76.4(Physics, Multidisciplinary)

We present in situ (X-ray diffraction) and ex situ (quenching) structural studies of crystalline, liquid, and glassy B$$_{2}$$O$$_{3}$$ up to 9 GPa and 1700 K, drawing equilibrium and nonequilibrium phase diagrams of B$$_{2}$$O$$_{3}$$, Particularly, we have determined the melting curve, the stability regions for crystalline B$$_{2}$$O$$_{3}$$ and B$$_{2}$$O$$_{3}$$ II modifications, the regions of transformations, such as densification or crystallization, for both the liquid and glassy states, including the region of sharp first-order-like transition in liquid B$$_{2}$$O$$_{3}$$ to a high-density phase near 7 GPa. Quenching experiments also show that the transition to the high-density liquid can occur at much lower pressures in nonstoichiometric melts with an excess of boron. B$$_{2}$$O$$_{3}$$ is the first glassformer whose transformations in the disordered state have been comparatively studied for both liquid and glassy phases.

Oral presentation

Structural study of liquid gallium under pressure

Yagafarov, O.; Katayama, Yoshinori; Brazhkin, V. V.*; Lyapin, A. G.*; Saito, Hiroyuki

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22 (Records 1-20 displayed on this page)