Ауксетичні властивості кристалів гексагональної сингонії

Pointing auxeticity surfaces of Be, Zn, MoS2, MnAs, TiB2 and BeCu (2,4 atm. % Cu) single crystals of hexagonal system were plotted for the first time using the experimental values of the elastic modulus , which given in the tables Landolt-Bernstein. The criteria of appearance of axial and noaksial auxeticity were established. The influence of alloying and temperature on effects of Be abnormal deformation was detected. The mechanisms of auxeticity properties formation in hexagonal crystals were established.Вперше побудовані вказівні поверхні ауксетичності монокристалів гексагональної сингонії Be, Zn, MoS2, MnAs, TiB2 та BeCu (2,4 ат.% Cu), використовуючи експериментальні значення модулів пружності , які наведені в таблицях Ландольт-Бернштейна. Встановлені умови виникнення аксіальної і неаксіальної ауксетичності. Виявлений вплив легування і температури на ефекти аномальної деформації Be. Встановлено механізми формування ауксетичних властивостей в гексагональних кристалах

Physical properties of thermoelectric zinc antimonide using first-principles calculations

We report first principles calculations of the structural, electronic, elastic and vibrational properties of the semiconducting orthorhombic ZnSb compound. We study also the intrinsic point defects in order to eventually improve the thermoelectric properties of this already very promising thermoelectric material. Concerning the electronic properties, in addition to the band structure, we show that the Zn (Sb) crystallographically equivalent atoms are not exactly equivalent from the electronic point of view. Lattice dynamics, elastic and thermodynamic properties are found to be in good agreement with experiments and they confirm the non equivalency of the zinc and antimony atoms from the vibrational point of view. The calculated elastic properties show a relatively weak anisotropy and the hardest direction is the y direction. We observe the presence of low energy modes involving both Zn and Sb atoms at about 5-6 meV, similarly to what has been found in Zn4Sb3 and we suggest that the interactions of these modes with acoustic phonons could explain the relatively low thermal conductivity of ZnSb. Zinc vacancies are the most stable defects and this explains the intrinsic p-type conductivity of ZnSb.Comment: 33 pages, 8 figure

Polarization-correlation optical microscopy of anisotropic biological layers

The theoretical background of azimuthally stable method of Jones-matrix mapping of histological sections of biopsy of myocardium tissue on the basis of spatial frequency selection of the mechanisms of linear and circular birefringence is presented. The diagnostic application of a new correlation parameter - complex degree of mutual anisotropy - is analytically substantiated. The method of measuring coordinate distributions of complex degree of mutual anisotropy with further spatial filtration of their high- and low-frequency components is developed. The interconnections of such distributions with parameters of linear and circular birefringence of myocardium tissue histological sections are found. The comparative results of measuring the coordinate distributions of complex degree of mutual anisotropy formed by fibrillar networks of myosin fibrils of myocardium tissue of different necrotic states - dead due to coronary heart disease and acute coronary insufficiency are shown. The values and ranges of change of the statistical (moments of the 1st - 4th order) parameters of complex degree of mutual anisotropy coordinate distributions are studied. The objective criteria of differentiation of cause of death are determined

The Impact of d– and f–compression on Anisotropy of Elastic Properties of Single Crystals with Hexagonal Close Packing of Lattice

Characteristic surfaces of Young's moduli were created usingtheory of elasticity of anisotropic crystals and computer processing of experimental data and patterns of their formationwere established. Detailed analysis of anisotropy of elastic properties of single crystals of transition metals with hexagonal close packing of lattice were conducted. Theimpact of d– and f–compression on anisotropy of elastic properties was discovered for the first time. A correlation between the anisotropy of elasticity and other physical properties of transition metals was established