共查询到20条相似文献,搜索用时 31 毫秒
1.
E. L. Gromnitskaya O. V. Stal'gorova A. G. Lyapin V. V. Brazhkin O. B. Tarutin 《JETP Letters》2003,78(8):488-492
Nonequilibrium phase transformations in D2O ices, including the solid-state amorphization of ice 1h (1h-hda) and the heating-induced transition cascade hda-lda-1c-1h from high-density amorphous (hda) ice to low-density amorphous (lda) ice followed by crystallization in cubic ice 1c and phase transition to ordinary hexagonal ice 1h, were studied using an ultrasonic technique. It has been shown that, as in H2O ice, the softening of a crystal lattice or an amorphous network precedes nonequilibrium transformations. However, noticeable isotopic differences in the behavior of the elastic properties of H2O and D2O, in particular, their 1h and hda modifications, call for a more detailed study of the structural features of these H2O and D2O phases. 相似文献
2.
E. L. Gromnitskaya O. V. Stal’gorova V. V. Brazhkin 《Journal of Experimental and Theoretical Physics》1997,85(1):109-113
The elastic characteristics of ice up to pressures of 1.7 GPa are determined for the first time at a temperature of 77 K,
along with features of their variation associated with the phase transformation of hexagonal ice Ih into high-density amorphous ice hda. The elastic instability of the ice lattice before solid-phase amorphization is experimentally confirmed. Elastic instability
during a transition from one amorphous state to another amorphous state was also observed for the first time; this took place
when hda ice was warmed at p=0.05 GPa from T=77 K.
Zh. éksp. Teor. Fiz. 112, 200–208 (July 1997) 相似文献
3.
A. I. Kolesnikov V. V. Sinitsyn O. I. Barkalov E. G. Ponyatovsky V. K. Fedotov A. M. Balagurov 《高压研究》2013,33(1-3):101-109
Abstract The transitions of the recovered high-pressure phase ice VIII first to high-density amorphous (hda) and low-density amorphous ices, and finally to cubic Ic, and hexagonal Ih ice were observed at heating using real-time neutron diffraction. Inelastic incoherent neutron scattering measurements on the hdu ice, ice Ih and high-pressure phase ice VI revealed similarity between the amorphous phase and crystalline ice VI and led to the new proposition that hda ice consists of two interpenetrating hydrogen-bounded networks with no hydrogen bonds between “sublattices”. 相似文献
4.
A. G. Lyapin O. V. Stal’gorova E. L. Gromnitskaya V. V. Brazhkin 《Journal of Experimental and Theoretical Physics》2002,94(2):283-292
A detailed investigation of different scenarios of structural transformations of H2O Ih ice during compression to a pressure of 2 GPa in the temperature range from 77 to 200 K is performed. In the range of temperatures and pressures being treated, detailed data are obtained for the density and the shear modulus for different phases of ice including the hda, IX, and XII phases. The experimentally obtained correlations for the density and ultrasonic velocities, with due regard for the available data of structural investigations, are used to identify the transformation sequences Ih→hda (below 135 K), Ih→II→VI (above 165 K), and Ih→IX→VI (from 155 to 180 K). In the vicinity of the crystallization temperature of amorphous ice, i.e., at about 140 K, an anomalous transformation pattern is observed, which is interpreted as predominantly the Ih→XII phase transition. The temperature crossover is discussed between the mode of solid-phase amorphization (Ih→hda) and crystal-crystal transitions, as well as the metastable nature of IX ice and the mechanism of solid-phase amorphization. 相似文献
5.
Shingo Kanehira Masaaki Sakakura Yasuhiko Shimotsuma Masaaki Eida Kiyotaka Miura Kazuyuki Hirao 《Applied Physics A: Materials Science & Processing》2010,101(1):81-85
Phase control of Fe–Si amorphous thin film in micro area is demonstrated using femtosecond laser irradiation. A femtosecond
laser beam with a high repetition rate over 200 kHz and tightly focused through an objective lens promotes both crystallization
and phase transformation from an amorphous phase into crystalline β-FeSi2, α-FeSi2, or ε-FeSi phases. Formation of each crystalline phase is possible by changing the pulse energy or the scanning speed of the incident
laser beam. 相似文献
6.
V. B. Efimov A. N. Izotov A. A. Levchenko L. P. Mezhov-Deglin S. S. Khasanov 《JETP Letters》2011,94(8):621-625
The structure of ice samples formed in the decay of a water impurity gel at temperatures above 4 K and atmospheric pressure
has been examined. The X-ray diffraction analysis indicates that three phases coexist in the initial sample at temperatures
of 85–110 K. These phases are amorphous ice occupying up to 30% of the sample volume, cubic-phase ice I
c metastable at low pressures (∼60%), and normal hexagonal ice I
h (≤6%). The characteristic sizes of crystals of the cubic and hexagonal phases are about 6 and 30 nm, respectively. The amorphous
phase at annealing above 110 K is gradually transformed to the crystalline phase both cubic and hexagonal. This transition
is accompanied by two processes, including a fast increase in the sizes of cubicphase nanocrystals and the partial transition
of the cubic phase I
c to the hexagonal one I
h. Hexagonal ice I
h prevails in the bulk of the sample above 200 K. 相似文献
7.
《Physics letters. A》2006,356(3):246-250
By using molecular dynamics (MD) simulations we found a transition from a tetrahedral to an octahedral network structure in an amorphous SiO2 model under compression from 2.20 to 5.35 g/cm3. And on heating of a high density amorphous (hda) model of 5.35 g/cm3 at zero pressure, the structure transforms to a low density amorphous (lda) form. Simulations were done in a model containing 3000 particles under periodic boundary conditions with interatomic potentials which have a weak Coulomb interaction and a Morse type short-range interaction. 相似文献
8.
Murat Durandurdu 《哲学杂志》2020,100(14):1818-1833
ABSTRACT We investigate the pressure-induced structural phase transformation of amorphous silicon hexaboride (a-SiB6) using a constant pressure first principles approach. a-SiB6 is found to undergo a gradual phase transformation to a high-density amorphous phase (HDA) in which the average coordination number of both B and Si atoms is about 6. The HDA phase consists of differently coordinated motifs ranging from 4 to 8. B12 icosahedra are found to persist during compression of a-SiB6 and the structural modifications primarily occur around Si atoms and in the regions linking pentagonal pyramid-like configurations to each other. Upon pressure release, an amorphous structure, similar to the uncompressed one, is recovered, indicating a reversible amorphous-to-amorphous phase change in a-SiB6. When the electronic structure is considered, the HDA phase is perceived to have a wider forbidden band gap than the uncompressed one. 相似文献
9.
T. D. Varfolomeeva S. V. Popova A. G. Lyapin V. V. Brazhkin S. G. Lyapin Yu. P. Kudryavtsev S. E. Evsyukov 《JETP Letters》1997,66(4):255-260
Structural transformations of the cumulene form of amorphous carbyne which are induced by heating at high pressure (7.7 GPa)
are investigated. These can be described by the sequence amorphous phase — crystal — amorphous phase — disordered graphite.
Raman scattering shows that predominately the chain structure of carbyne remains at the first three stages. It was found that
the intermediate crystalline phase is an unknown modification of carbon whose structure is identified as cubic (a=3.145 Å). A mechanism of structural transformations in carbyne that involves the formation of new covalent bonds between
chains is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 237–242 (25 August 1997) 相似文献
10.
Abstract We investigate the phase transformations in sulfur for pressures up to 10 GPa by time resolved Raman spectroscopy. The transition to the photosensitive phase p-S is stimulated by the blue laser line between 3 and 9 GPa. The kinetics of this transition as derived from the time evolution of the intensities of characteristic Raman excitations shows the typical features of an activated first order phase transition. This transformation proceeds via a disordered (amorphous) intermediate state. Above 9 GPa a further phase change to S, is kinetically characterized and follows similar rules i.e. the integral intensities of selected S, Raman lines exhibit a sigmoidal time dependence. In both high pressure phases a broad Raman excitation between 800 and 1000 cm?1 is observed. 相似文献
11.
K. Wang H. Lee R. Cooper H. Liang 《Applied Physics A: Materials Science & Processing》2009,95(2):435-441
We investigate the time-dependent and anisotropic phase transformation of poly (vinylidene difluoride) (PVDF) under bending.
Using combined techniques of an atomic force microscope and a Fourier transform infrared spectroscope, observation of surface
morphology and phase transformation in time was made. Results showed that bending stress induces the transformation of amorphous,
α,β, and γ crystalline phases. Specifically, the amorphous phase was transformed into the β phase when the bending force was applied. In addition, the transformation observed was time and direction dependent. The
anisotropic behavior observed brings insights into the origin of the piezoelectricity of PVDF. 相似文献
12.
M. A. Khusainov 《Technical Physics》1997,42(6):692-694
The stress-strain behavior of a round plate during thermal cycling through the range for martensitic phase transformations
is investigated. It is shown that the plate loses stability and recovers its original shape with a clap when a certain temperature
A
in<T
ls⩽A
fin is reached. The results of measurements of the impact and reactive forces are presented. The conditions for the occurrence
of a clap are determined.
Zh. Tekh. Fiz. 67, 118–120 (June 1997) 相似文献
13.
This paper discusses amorphous TbxCr100−x
alloys (x=16, 28.5, 43, and 59 at.%) obtained by quenching from the vapor phase. It is found that the structure of the alloys is heterogeneous:
the coexistence of two amorphous phases, characterized by different short-range order, is observed. The short-range order
of these phases qualitatively corresponds to the structure of pure components (Cr or Tb). In the low-temperature region, the
alloys transform to the spin-glass state. It is established that the transition temperatures to the spin-glass state depends
on the composition linearly, increasing as the terbium concentration increases. It is shown that the magnetic properties of
amorphous Tb-Cr alloys are determined by the random magnetic anisotropy associated with the Tb atoms.
Fiz. Tverd. Tela (St. Petersburg) 41, 1236–1239 (July 1999) 相似文献
14.
A. M. Glezer G. I. Nosova R. V. Sundeev A. V. Shalimova 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(11):1515-1521
X-ray diffraction and transmission electron microscopy were used to study features of the structural and phase transformations
of initially crystalline T150Ni25Cu25 alloy upon severe plastic deformation in a Bridgman cell. Three cycles of successive phase transitions of the crystal ⟹ amorphous
state and amorphous state ⟹ crystal type were revealed under continually increasing deformation. The results are explained
within the superposition of different channels of elastic energy dissipation at severe plastic deformation. 相似文献
15.
Based on the newly developed coherent-entangled state representation,we propose the so-called Fresnel-Weyl complementary transformation operator.The new operator plays the roles of both Fresnel transformation(for(a 1 a 2)/√ 2) and the Weyl transformation(for(a 1 + a 2)/√ 2).Physically,(a 1 a 2)/√ 2 and(a 1 + a 2)/√ 2 could be a symmetric beamsplitter’s two output fields for the incoming fields a 1 and a 2.We show that the two transformations are concisely expressed in the coherent-entangled state representation as a projective operator in the integration form. 相似文献
16.
The low-temperature specific heat of a La1.85Sr0.15CuO4 superconducting single crystal was investigated in magnetic fields up to 8 T and with four orientations — in the a-b plane (along the (100) and (110) directions) and at angles of 45° and 90° with respect to the a-b plane (along the (103) and (001) directions). Anisotropy was observed in the field dependence of the specific heat in the
a-b plane. The specific heat was found to be minimum with the field oriented in the direction of the a axis and maximum with the field oriented in a direction making an angle of 45° with the a axis. This can be explained by the anisotropy of the energy gap, whose minimum lies along the (110) direction. For all orientations
of the magnetic field the specific heat of the mixed state at low temperatures is a nonlinear function of the magnetic field
strength.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 683–687 (10 December 1997) 相似文献
17.
2-(p-N,N-dimethylaminostyryl)benzoxazole (OS), 2-(p-N,N-dimethylaminostyryl)-benzothiazole (SS) and 2-(p-N,N-dimethylaminostyryl)naphtiazole (PS) were prepared and their absorption and fluorescence spectra were measured in various solvents at room temperature. On the basis of the solvatochromic behavior the ground state (μg) and excited state (μe) dipole moments of these pN,N-dimethylaminostyryl derivatives were evaluated. The dipole moments (μg and μe) were estimated from solvatochromic shifts of absorption and fluorescence spectra as function of the dielectric constant (ɛ) and refractive index (n) of applied solvents. The absorption spectra only slightly are affected by the solvent polarity in contrast to the fluorescence spectra that are highly solvatochromic and display a large Stokes shift. The analysis of the solvatochromic behavior of the fluorescence spectra as function of Δf (ɛ, n) revealed that the emission occurs from a high polarity excited state. The large dipole moment change along with the strongly red-shifted fluorescence, as the solvent polarity is increased, demonstrate the formation of an intramolecular charge transfer state (ICT). Compounds under the study were used as fluorescence probes for monitoring the kinetics of polymerization. The study on the changes in fluorescence intensity and spectroscopic shifts of studied compounds were carried out during thermally initiated polymerization of methyl methacrylate (MMA) and during photoinitiated polymerization of 2-ethyl-2-(hydroxymethyl)propane-1,3-diol triacrylate (TMPTA). 相似文献
18.
V. V. Brazhkin A. G. Lyapin R. N. Voloshin S. V. Popova Yu. A. Klyuev A. M. Naletov S. C. Bayliss A. V. Sapelkin 《JETP Letters》1999,69(11):869-875
The results of an investigation of the transformation of C60 fullerite to diamond under pressure through intermediate three-dimensionally polymerized and amorphous phases are reported.
It is found that treatment of fullerite C60 at pressures 12–14 GPa and temperatures ∼1400°C produces a nanocrystalline graphite-diamond composite with a concentration
of the diamond component exceeding 50%. At lower temperatures (700–1200°C) nanocomposites consisting of diamondlike (sp
3) and graphitic (sp
2) amorphous phases are formed. The nanocomposites obtained have extremely high mechanical characteristics: hardness comparable
to that of best diamond single crystals and fracture resistance two times greater than that of diamond. Mechanisms leading
to the transformation of C60 fullerite into diamond-based nanocomposites and the reasons for the high mechanical characteristics of these nanocomposites
are discussed.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 11, 822–827 (10 June 1999) 相似文献
19.
V. P. D’yakonov V. I. Markovich V. L. Kovarskii A. V. Markovich M. Borowiec A. Jedrzejczak H. Szymczak 《Physics of the Solid State》1998,40(4):691-698
The low-temperature thermal and magnetic-resonance properties of a monoclinic KDy(WO4)2 single crystal are investigated. It is established that a structural phase transition takes place at T
c=6.38 K. The field dependence of the critical temperature is determined for a magnetic field oriented along the crystallographic
a and c axes. The initial part of the H-T phase diagram is plotted for H∥a. The prominent features of the structural phase transition are typical of a second-order Jahn-Teller transition, which is
not accompanied by any change in the symmetry of the crystal lattice in the low-temperature phase. The behavior of C(T) in a magnetic field shows that the transition goes to an antiferrodistortion phase. An anomalous increase in the relaxation
time (by almost an order of magnitude) following a thermal pulse is observed at T>T
c(H), owing to the structural instability of the lattice. A theoretical model is proposed for the structural phase transition
in a magnetic field, and the magnetic-field dependence of T
c is investigated for various directions of the field.
Fiz. Tverd. Tela (St. Petersburg) 40, 750–758 (April 1998) 相似文献
20.
X-ray diffraction is used to study the temperature dependence of the lattice parameters and the sequence of structural realignments
in crystalline Rb2ZnCl4 over temperatures of 4.2–310 K. The appearance of and changes in the system of satellite reflexes indicative of structural
ordering are studied. Below 74 K, on going into the monoclinic phase (space group A11a), anomalies are observed in the behavior of the lattice parameters, and superstructural reflexes develop with wave vectors
q=a
*/3+b
*/2+c
*/2 corresponding to an increase by a large factor in initial parameters a, b, and c of the Pnma-phase.
Fiz. Tverd. Tela (St. Petersburg) 41, 1084–1090 (June 1999) 相似文献