A method for calculating the parameters of formation of vacancies in crystals formed by spherically symmetrical atoms was developed. Both quantum effects at low temperatures and the possibility of the delocalization of atoms at high temperatures were studied. The parameters of formation of vacancies in carbon subgroup element crystals C-diam, Si, Ge, α-Sn, and Pb were calculated. The inclusion of the delocalization of atoms was shown to increase the enthalpy, entropy, and volume of vacancy formation. At low temperatures, the parameters of vacancy formation were found to depend strongly on the temperature, and the entropy of vacancy formation became negative. At high temperatures, close agreement with experimental data and theoretical estimates reported by other authors was obtained. The temperature dependence of vacancy parameters was studied for diamond heated isobarically from 100 to 4500 K. The applicability scope of the Arrhenius equation with a temperature-independent activation energy is discussed. The validity of the “compensation rule” (correlation between the entropy and enthalpy of vacancy formation) was demonstrated. It was also shown that the volume and entropy of vacancy formation were correlated over the whole temperature range studied.
The charged particle multiplicity distribution has been studied for non-single-diffractive π+p andpp collisions at \(\sqrt s = 22\) GeV, for full phase space as well as for intervals in rapidity, azimuthal angle and transverse momentum. In general, the multiplicity distribution is well described by a negative binomial. From comparison of the distribution for negative or positive particles to that of all charged particles, cascading is favoured as an interpretation over stimulated emission. Interesting consequences follow from a comparison of our results to those at collider energies and toe+e? data at comparable energy. Furthermore, evidence is given that the multiplicity distribution is not exactly of negative binomial type in every (connected or disconnected) phase space region. 相似文献
Forward-backward multiplicity correlations in σ+,K+p andpp collisions at 250 GeV/c ( \(\sqrt s \) =22 GeV) are given for all charges and for the different charge combinations. The correlations are found to be caused predominantly by centrally produced particles. It is demonstrated that this result is an agreement with observations at the ISR and the CERNp \(\bar p\) -Collider. The results are compared to expectations from LUND, DPM and FRITIOF Monte Carlo models and a geometrical picture relating correlations in hadron-hadron collisions toe+e? data in terms of impact parameters is tested. 相似文献
[reaction: see text] Chemoselective cyclizations of divinyl ketones to cyclohexenones mediated by a sterically demanding Lewis acid and an amine base have been accomplished under mild reaction conditions. The extension of this methodology to the synthesis of eight-membered rings is also demonstrated. 相似文献
We have studied the photoelectric properties of the potential barrier which arises at the interface between an electrolyte and thin n-CuInSe2 films deposited on glass by vacuum evaporation. Photoelectrochemical cells were used to observe the rectification and photosensitivity near the fundamental absorption of CuInSe2 for photon energies >1 eV. It was found that there is a correspondence between the spectral dependence of the absorption and the photosensitivity of the cells, which indicates a constant quantum efficiency for the photoconversion process. We conclude with a discussion of the practical application of the potential barriers studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 24–26, February, 1992. 相似文献
For a fixed temperature of 300 K on a specimen of CdSnAs2Cu acted upon by a uniform pressure of up to 1.5 GPa, the dependence of the thermo-electromotive force on the narrow band population is studied for the first time. In agreement with theory, the sign of the thermo-electromotive force is observed to change sign in the studied crystals. The limits of the validity of the narrow band approximation are refined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 116–119, September, 1991. 相似文献