Моделирование одноосной деформации нанокристаллов магния "жесткой " и "мягкой" ориентировок

Atomistic modeling of high-speed deformation by compression of ideal, defective (5% vacancies, 5% impurity hydrogen atoms) magnesium nanocrystals with "hard" and "soft" orientations at T = 300 – 375 K was carried out. Three interatomic interaction potentials were used. The evolution of the microrelief of the free surface of magnesium nanocrystals in the process of plastic flow is shown. Diagrams "stress σ – deformation ε" are constructed, deformation dependences of the scalar dislocation density are determined, and the strain rate dependences on the degree of deformation ε are constructed. The influence of vacancies and hydrogen atoms on the shape of deformation curves, dislocation structure and scalar dislocation density is shown. Evolution of typical dislocation structures is shown, some typical dislocation reactions are given. Conclusions are drawn on the influence of the type of interatomic interaction potential on the calculated characteristics.

Ab initioX-ray structural characterization of an inclusion compound with a compositionally disordered chiral guest: no prior knowledge of the crystal composition

The crystal structure and absolute configuration of a molecular host/guest/impurity inclusion complex were established unequivocally in spite of our having no prior knowledge of its chemical composition. The host (4R,5R)-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-1,3-dioxolane, (I), displays expected conformational features. The crystal-disordered chiral guest 4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one, (II), is present in the crystal 85.1 (4)% of the time. It shares a common site with 4a-hydroperoxymethyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one, (III), present 14.9 (4)% of the time, which is the product of autoxidation of (II). This minor peroxide impurity was isolated, and the results of nuclear magnetic resonance, mass spectrometry, and X-ray fluorescence studies are consistent with the proposed structure of (III). The complete structure was therefore determined to be (4R,5R)-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-1,3-dioxolane–4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one–4a-hydroperoxymethyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one (1/0.85/0.15), C31H30O4·0.85C10H14O·0.15C10H14O3, (IV). There are host–host, host–guest, and host–impurity hydrogen-bonding interactions of typesSandDin the solid state. We believe that the crystals of (IV) were originally prepared to establish the chirality of the guest (II) by means of X-ray diffraction analysis of host/guest crystals obtained in the course of chiral resolution during cocrystallization of (II) with (I). In spite of the absence of `heavy' elements, the absolute configurations of all anomeric centres in the structure are assigned asRbased on resonant scattering effects.