[en] Highlights: ► A new package for calculating elastic constants of orthorhombic structure is released. ► The package called ortho-elastic. ► It is compatible with [FP-(L)APW+lo] method implemented in WIEN2k code. ► Several orthorhombic structure compounds were used to test the new package. ► Elastic constants calculated using this package show good agreement with experiment. - Abstract: A new package for calculating the elastic constants of orthorhombic structure is released. The package called ortho-elastic. The formalism of calculating the ortho-elastic constants is described in details. The package is compatible with the highly accurate all-electron full-potential (linearized) augmented plane-wave plus local orbital [FP-(L)APW+lo] method implemented in WIEN2k code. Several orthorhombic structure compounds were used to test the new package. We found that the calculated elastic constants using the new package show better agreement with the available experimental data than the previous theoretical results used different methods. In this package the second-order derivative E^″(ε) of polynomial fit E=E(ε) of energy vs strains at zero strain (ε=0), used to calculate the orthorhombic elastic constants.

[en] This paper seeks to provide a number of reformulations of the quasi-implicative conditions which are more intuitively plausible. Three sets of conditions are examined, and it is shown that each set of conditions is both necessary and sufficient to ensure that an ortholattice is orthomodular, and each set of conditions uniquely specifies the implication operation to be Mittelstaedt's quasi-implication. Various properties of the quasi-implication are then investigated. In particular, it is shown that the quasi-implication fails to satisfy a number of laws associated with the classical material conditional. Various weakenings of these laws, satisfied by the quasi-implication, are also discussed. (orig./BJ)

[en] An algebraic approach is developed to derive space groups using 4x4 Seitz matrices for the crystal classes mm2, 222 and mmm in the orthorhombic system. The advantage of the present method is that it is relatively simple and can be adapted to introduce space groups to beginners. One of the advantages of the present method is that it admits a geometrical visualization of the symmetry elements of space group. The method can easily be extended to other crystal classes in a straightforward way. 16 refs, 1 fig., 2 tabs

[en] The possibility to prepare directly in air superconducting YBCO samples showing T_c,0 above 90 K is reported and discussed. The most critical parameter in determining the final T_c is represented by the cooling rate in the lower temperature region, characterised by a lower oxygen mobility. The results point out that the partial pressure of oxygen in air is sufficient to assure the formation of the orthorhombic phase with an oxygen content as high as 6.96

[en] A procedure for calculating antiferromagnetic resonance (AFMR) frequencies is discussed in which a new form of the magnetohydrodynamic equations is employed. As an example, orthorhombic antiferromagnets with an orthoferrite-type magnetic exchange structure are considered. The application to antiferromagnets with other crystallographic and magnetic structures is discussed. (reviews of topical problems)

[en] The effective elastic constants of a superlattice composed of layers of orthorhombic symmetry (with principal axes along the superlattice axis) are derived. These results generalize previous determinations for elastically isotropic layers (Rytov, Akust. Zh. 2, 71 (1956) [Sov. Phys.: Acoust. 2, 68 (1956)]), but a completely different approach is used

[en] Cyclotrimethylene trinitramine (RDX) crystalizes in the orthorhombic α-phase at the ambient pressure and temperature. In principle, the point defects commonly found in monatomic crystals, such as vacancies and interstitials, may exist in RDX as well. However, in molecular crystals one encounters additional point defects associated with the distortion of the molecules. A set of rotational defects are described in this article. These are molecules which are located in the proper positions in the crystal but are rotated relative to the molecules in the perfect crystal, and their ring is slightly puckered. The energetic barriers for defect formation and for their annealing back to the perfect crystal configuration are computed using an atomistic model. It is shown that the formation energy of rotational defects is smaller than the vacancy formation energy. Such defects are identified in the cores of dislocations in RDX and hence their concentration in the crystal is expected to increase during plastic deformation. The importance of such point defects is related to their role in phonon scattering and in dislocation-mediated plastic deformation

[en] Highlights: • A thermochemical explanation for the stability of the unusual sodium chlorides NaCl₃ and NaCl₇ is provided, based on lattice energy values. • By using the generalized Glasser-Jenkins equation [3] lattice energies (kJ mol⁻¹) of −162.5, −168.9 and −113.1 are calculated for Pm3n NaCl₃, Pnma NaCl₃ and NaCl₇, respectively. Thermodynamically stable cubic and orthorhombic NaCl3 as well as NaCl₇ have been synthesized (Zhang et al., 2013). In the present work, a thermochemical explanation for the stability of such unusual sodium chlorides is provided, based on lattice energy values. Using the Glasser-Jenkins generalized equation (Glasser and Jenkins, 2000) lattice energies (kJ mol⁻¹) of −162.5, −168.9 and −113.1 are calculated for Pm3n NaCl₃, Pnma NaCl₃ and NaCl₇, respectively. It is postulated that any Na_xCl_y compound could be synthesized, if the ionic character of the NaCl bond in the prepared compound remains around 80%, and the sodium charge below unit.

[en] A classification of acoustic-beam reflection resonances in orthorhombic crystals under conditions where a proximity to conversion is implemented in the vicinity of total internal reflection is proposed. In this case, the energy from the incident pump beam falls almost entirely into a narrow intense reflected beam propagating at a small angle with respect to the surface. The crystal boundary is parallel to one of the elastic symmetry planes, and the excited beam propagates near one of axes 2 in this plane. Depending on the relations between the elastic moduli and the chosen propagation geometry, 18 types of resonances may occur, but no more than three in each crystal. The developed theory combines an approximate analytical description and accurate computer analysis. The relations between the elastic moduli providing minimum energy loss over the parasite reflected wave are determined. Some crystals with resonant excitation very close to conversion are revealed.

[en] The hydrothermal synthesis and single crystal structure of Zn₃(HPO₃)₄·Zn(H₂O)₆ are reported. The structure is built-up from vertex linking ZnO₄ tetrahedral and HPO₃ pseudo-pyramids units, giving rise to a three-dimensional framework with large 8, 16-membered ring channels. The zincophosphite is purly inorganic with the octahedral zinc complex filled in the channel. The synthesis of system required the presence of the organic amine which is not incorporated into the structure of the product. The framework-metal complex encapsulating in the channel is the first time appeared in open-framework zincophospates and zincophosphites. Crystal data: Zn₃(HPO₃)₄·Zn(H₂O)₆, M=689.52, orthorhombic, Fddd (No. 70), a=9.679(4) A, b=11.926(5) A, c=30.691(12) A, V=3543(2) A³, Z=8, ρ_cacl=2.585 Mg/m³, μ=5.798 cm^-1, R=0.0265, R_w=0.0406