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61.
As part of a study of defect tetrahedral structure compounds, the elastic constants of single crystal specimens of Hg3Ga2□Te6 and HgIn2□Te4 have been measured between 77 K and room temperature using the pulse superposition technique. These compounds are included in the series HgTe, Hg5In2□Te8, Hg3In2□Te6 and HgIn2□Te4 and HgTe, Hg5Ga2□Te8, Hg3Ga2□Te6 where there is a progressive increase in the concentration of vacant sites. While the other compounds studied are cubic, HgIn2□Te4 has a tetragonal structure with a ratio of 2.0. The components of the elastic stiffness tensor of this material at 77 K are (in units of 1011 dyne cm?2) C11 = 4.31 C12 = 2.54 C44 = 2.14 C33 = 4.47 C13 = 2.18 C66 = 2.41. In a cubic material C11 = C33, C44 = C66 and C12 = C13: the elastic behaviour of this tetragonal compound closely resembles that of a cubic material, as might be anticipated from its structure. This similarity is further illustrated by reference to the symmetry of phase velocity and Young's modulus surfaces. Examination of the elastic constants and reduced elastic constants of these compounds shows a regular trend, the elastic stiffness decreases as the number of vacant sites increases. There is an approximately linear relationship between the reduced bulk modulus and the number of sited vacancies. 相似文献
62.
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64.
Y.K. Yoḡurtçu A.J. Miller G.A. Saunders 《Journal of Physics and Chemistry of Solids》1981,42(1):49-56
The six third order elastic constants of GaP have been obtained from measurements of the effect of hydrostatic and uniaxial pressures on ultrasonic wave velocities. The valence force field model has been used to obtain the bond-bending and stretching force constants. Confirmatory evidence is added to the hypotheses that zinc blende structure crystals undergo the densification transition under pressure when (1) a modified Born stability criterion that equals about 0.2 is reached at the phase transition pressure Pt, and (2) the ratio of the second order bond-bending βt to bond-stretching αt, force constants is about 0.1. These findings suggest that a macroscopic shear takes place at the transition 相似文献
65.
Hydrostatic-pressure derivatives of the elastic stiffness constants have been measured ultrasonically in a bcc InTl alloy of composition near the eutectoid. The shear modulus is small, but does not soften under pressure: the eutectoid reaction is not directly associated with a mode softening shear instability. Anharmonic contributions to the excess vibrational entropy from the q 〈110〉, e 〈10〉 modes which stabilize the bcc structure are small compared with the harmonic contributions. 相似文献
66.
A broad absorption peak dominates the ultrasonic loss in sodium borosilicate glasses below room temperature; a subsidiary peak occurs at liquid helium temperatures. The broad peak and its counterpart in vitreous silica are shown to be consistent with a structural relaxation process rather than an Akhieser type phonon-phonon interaction. 相似文献
67.
The oxidations of 2,3,4-trimethylaniline, 4-isopropyl-2,6-dimethylaniline, 4-t-butyl-2,6- dimethylaniline and 4-cyclohexyl-2,6-dimethylaniline by peroxidase have been studied in detail. In three instances alkyl group migrations are involved and a mechanism is proposed. 相似文献
68.
69.
R.E. Ballard S.L. Barker J.J. Gunnell W.P. Hagan S.J. Pearce R.H. West A.R. Saunders 《Journal of Electron Spectroscopy and Related Phenomena》1978,14(5):331-339
Nine bands in the He(I) gas-phase photoelectron spectrum of 1,2-ethanediol are assigned by means of ab initio calculation and by comparison with the sp 相似文献
70.