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1.
Abstract The changes in the characteristics of vibrational and optical properties of the conducting form of polypyrrole under pressure is studied. 相似文献
2.
A novel two-color photoluminescence (PL) is found in MnF(2) at room temperature under high pressure. Contrary to low-temperature PL, PL at room temperature is unusual in transition-metal concentrated materials like MnF(2), since the deexcitation process at room temperature is fully governed by energy transfer to nonradiative centers. We show that room-temperature PL in MnF(2) originates from two distinct Mn(2+) emissions in the high-pressure cotunnite phase. The electronic structure and the excited-state dynamics are investigated by time-resolved emission and excitation spectroscopy at high pressure. 相似文献
3.
The Raman spectrum of NH4I has been measured under hydrostatic pressure. The high pressure phase of NH4I was identified with the disordered CsCl-type phase by comparing the spectrum with that of NH4 Br. The mode-Grünesen parameters of NH4Br and NH4I were determined from the frequency shift of phonon bands under hydrostatic pressure. These values were compared with the thermodynamic value and that obtained from the Slater relation. Contributions to the thermodynamic Grüneisen constant are discussed from free energy terms of NH+4-orientation and -interactions with lattice modes. 相似文献
4.
Abstract We have measured the Raman spectra of the quasi-one-dimensional crystal SbSBr as a function of pressure at 295, 70, 37 and 25 K. The pressure coefficients of the observed Raman modes have been determined and used to distinguish inter-from intrachain modes. Spectral features characteristic of the ferroelectric phase have been attributed to impurities or lattice imperfections and not to the presence of the ferroelectric phase, providing indication that the para-to ferroelectric phase transition occurs below 25 K. 相似文献
5.
Walter F. Love Hans D. Hochheimer Mark W. Anderson Richard N. Work Charles T. Walker 《Solid State Communications》1977,23(6):365-368
The temperature dependence of the elastic constants of NaCN has been studied by propagation of ultrasonic waves at 15 MHz and by Brillouin scattering at 3 GHz over the temperature range from 287K to 355K. c44 is observed to soften linearly with temperature as the order-disorder phase transition at 284K is approached from above. The other elastic constants also soften, except for c12 which stiffens. Considerable dispersion is seen in the values of c44 obtained ultrasonically and by Brillouin scattering. Measurements of the temperature dependence of the density are also reported. 相似文献
6.
H. Fjellvåg A. Kjekshus T. Chattopadhyay H.D. Hochheimer W. Hönle H.G. Von Schnering 《Physics letters. A》1985,112(8):411-413
Energy dispersive high-pressure powder X-ray experiments have been performed for MnTe2 up to a pressure of 20 GPa. MnTe2 undergoes a discontinuous transformation from the cubic pyrite type structure to the orthorhombic marcasite type structure at 7.0±0.5 GPa upon increasing pressure. The transformation is accompanied by a large reduction in the specific volume (ΔV/V=0.18) which probably reflects different magnetic properties of the two modifications of MnTe2. 相似文献
7.
H. D. Hochheimer F. Widulle J. Th. Held G. Strehl R. T. Kotitschke A. R. Adams 《高压研究》2013,33(1-6):41-48
Abstract We present the design of a device for the simultaneous application of uniaxial stress and hydrostatic pressure. This new apparatus will for the first time allow measurements at constant strain. Results of the simultaneous application of uniaxial stress and hydrostatic pressure to a semiconductor laser are presented and discussed. 相似文献
8.
We report the results of electrical resistance measurements at high pressures on Cs2MoS4 and KTbP2Se6. The results of high pressure X-ray diffraction study of Cs2MoS4 are also presented. Interestingly, in the case of Cs2MoS4 the resistance vs. pressure follows the behavior of the absorption edge vs. pressure obtained from our optical measurements lending further support to a direct-indirect band crossing. In the case of KTbP2Se6,the phase transition at about 9.2 GPa is reflected in a sharp drop of the resistance. In addition we report the pressure dependence of the lattice constants as well as the equation of state of Cs2MoS4. 相似文献
9.
H. D. Hochheimer E. Gmelin W. Bauhofer Ch. von Schnering-Schwarz H. G. von Schnering J. Ihringer W. Appel 《Zeitschrift für Physik B Condensed Matter》1988,73(2):257-263
The real part of the dielectric constant , the heat capacityc
p, the infrared reflectivity, and the X-ray diffraction of TlGaSe2 have been measured in the temperature range from 12 K (30K) to 300 K. Both andc
p show two anomalies at about 110 K and 120 K. A study of the hysteresis loop as well as an investigation of the dielectric dispersion in the microwave region show that the phase below 110 K is ferroelectric. The crystal structure remains nearly unchanged in the course of the phase transition. The loss of the
symmetry (C2/cCc) results from small positional shifts of the T1 atoms in the ab plane accompanied by a discontinuity in the axial ratios. We suggest, that the ferroelectricity is caused by the stereochemically active electron lone pair configuration of the Tl+ ion. Thus TlGaSe2 may provide the first example for ferroelectricity caused by this mechanism. 相似文献
10.
Six new actinide metal thiophosphates have been synthesized by the reactive flux method and characterized by single-crystal X-ray diffraction: Cs(8)U(5)(P(3)S(10))(2)(PS(4))(6) (I), K(10)Th(3)(P(2)S(7))(4)(PS(4))(2) (II), K(5)U(PS(4))(3) (III), K(5)Th(PS(4))(3) (IV), Rb(5)Th(PS(4))(3) (V), and Cs(5)Th(PS(4))(3) (VI). Compound I crystallizes in the monoclinic space group P2(1)/c with a = 33.2897(1) A, b = 14.9295(1) A, c = 17.3528(2) A, beta = 115.478(1) degrees, Z = 8. Compound II crystallizes in the monoclinic space group C2/c with a = 32.8085(6) A, b = 9.0482(2) A, c = 27.2972(3) A, beta = 125.720(1) degrees, Z = 8. Compound III crystallizes in the monoclinic space group P2(1)/c with a = 14.6132(1) A, b = 17.0884(2) A, c = 9.7082(2) A, beta = 108.63(1) degrees, Z = 4. Compound IV crystallizes in the monoclinic space group P2(1)/n with a = 9.7436(1) A, b = 11.3894(2) A, c = 20.0163(3) A, beta = 90.041(1) degrees, Z = 4, as a pseudo-merohedrally twinned cell. Compound V crystallizes in the monoclinic space group P2(1)/c with a = 13.197(4) A, b = 9.997(4) A, c = 18.189(7) A, beta = 100.77(1) degrees, Z = 4. Compound VI crystallizes in the monoclinic space group P2(1)/c with a = 13.5624(1) A, b = 10.3007(1) A, c = 18.6738(1) A, beta = 100.670(1) degrees, Z = 4. Optical band-gap measurements by diffuse reflectance show that compounds I and III contain tetravalent uranium as part of an extended electronic system. Thorium-containing compounds are large-gap materials. Raman spectroscopy on single crystals displays the vibrational characteristics expected for [PS(4)](3)(-), [P(2)S(7)](4-), and the new [P(3)S(10)](5)(-) building blocks. This new thiophosphate building block has not been observed except in the structure of the uranium-containing compound Cs(8)U(5)(P(3)S(10))(2)(PS(4))(6). 相似文献