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31.
Reviakine I Georgiou DK Vekilov PG 《Journal of the American Chemical Society》2003,125(38):11684-11693
During layerwise growth of crystals, capillarity governs the generation of new crystal layers. Theory predicts that the line tension of the layer edge determines, via the characteristic two-dimensional capillary length L(c), the rates of generation and initial growth of the new layers. To test the correlation between L(c) and the rate of layer generation, we used in situ Tapping Mode Atomic Force Microscopy (TM-AFM) to study the generation and spreading of layers during crystallization of rhombohedral, R3, porcine insulin. We show that crystallization of this insulin form is uniquely suitable for such an investigation due to the linear kinetics of step growth it exhibits. This linear kinetics reflects the abundance of the incorporation sites along the rough steps, the lack of long-range step-step interactions, and the transport control of the growth kinetics. The kinetic coefficients are 7 x 10(-)(3) and 4 x 10(-)(2) cm s(-)(1), respectively, in the absence and presence of the cosolvent acetone-somewhat high for proteins and comparable to values for inorganic systems. We show that (i). the relevant capillary length, the size of a critical quadrangular 2D nucleus L(c), is the main scaling factor for the density of growth steps, while (ii). all steps longer than L(c) grow with a rate determined only by the supersaturation and independent of their length. We explain the divergence of (ii). from theoretical predictions with the high supersaturations typical of the growth of this protein system. 相似文献
32.
33.
Effect of phasons and magnetic fields on the electronic spectrum of a three-dimensional quasicrystal
The effect of phasons and magnetic fields on the electronic spectrum of an icosahedral quasicrystal is investigated in the
tight-binding approximation. Phasons smooth the singular spectrum and produce a greater delocalization of the critical wave
functions. A magnetic field shifts the limits of the spectrum, smooths the spectrum, lifts the degeneracy, and also delocalizes
the wave functions.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 9, 659–661 (10 May 1999) 相似文献
34.
Changes in zone structure of inert gas crystals with pressure are studied. The zone structure of solid Ne, Ar, Kr, and Xe are calculated over a wide pressure range using the combined plane wave method. Stability limits of the basic dielectric phase are determined by overlap of direct gaps in the electron spectrum with pressure increase. No loss of stability upon transition to the metallic state was observed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 68–74, March, 1984. 相似文献
35.
The electronic structure of a hydrogen atom in a 1/1 approximant of the Ti-Zr-Ni icosahedral quasicrystal is investigated using ab initio methods based on the density functional theory. The charge state of the hydrogen atom in Ti36Zr32Ni13 with different types of tetrahedral pores, as well as the charge state of hydrogen at a ratio H/M ≈ 1.7, is determined. The hydrogen atom is found to be in a nearly neutral state. The coefficient of hydrogen diffusion in Ti36Zr32Ni13 is calculated. 相似文献
36.
The degree of tetragonality of TiAl and the effect of vanadium doping on it are studied theoretically in the framework of the coherent-potential approximation using ab initio potentials. It is shown that substitution of vanadium for Ti increases the degree of tetragonality, whereas substitution of vanadium for aluminum decreases the degree of tetragonality of the TiAl: V alloy and the lattice becomes virtually cubic when the vanadium content is about 8 at. %; this, in turn, can increase the plasticity of TiAl, which is brittle at low temperatures. 相似文献
37.
A. S. Mikhailushkin É. I. Isaev Yu. Kh. Vekilov S. I. Simak 《Physics of the Solid State》2003,45(12):2213-2217
An ab initio study of the electronic structure and the Fermi surface is carried out for random Al-Si and Al-Ge solid solutions. At a 10 at. % Si content, a topological transition of the neck-formation type is revealed, which can account for the experimentally observed peculiarities of the transport properties of the Al-Si system. A similar transition is also found in the Al-Ge system, and the appearance of the anomalous transport coefficients at Ge concentrations of about 10 at. % is predicted. In addition, it is shown that the increase in the concentration of the dopants gives rise to nesting of the Fermi surface sheets (superposition of electron-hole pockets). This peculiarity of the Fermi surface can be responsible for the enhancement of the superconductivity and the instability of the crystal structure observed in the Al1?xSix and Al1?xGex solid solutions. 相似文献
38.
Phase stability boundaries for transition metals are derived from the condition of electron spectrum degeneration with respect to an external field. 相似文献
39.
The energy of hydrogen dissolution in different tetrahedral pores of a 1/1 approximant of the icosahedral TiZrHf quasicrystal has been determined in terms of the density functional theory and ab initio pseudopotentials. At low and high degrees of loading of TiZrHf with hydrogen, the charges of atoms involved in the system and the Mayer bond order have been calculated for all possible M-M and M-H pairs. The diffusion coefficient of a single hydrogen atom in the system under study has been estimated numerically. 相似文献
40.
A. Altshuler S. N. Bezryadin Yu. Kh. Vekilov V. D. Verner 《physica status solidi b》1981,106(2):447-459