Развитие метода локальной симметрии в модели суперъячейки для кристалла с примесью

The symmetry aspects of the supercell (extended primitive unit cell) model of the crystal with point defect are considered: Wyckoff positions splitting and the change of the one-electron states classification over k-vector (Brillouin zone folding). The supercell choice has to be made in a such a way that the one-electron states at the valence band top and the conduction band bottom for the perfect crystal are reproduced. Wyckoff positions splitting in the supercell model allows one to consider the defective crystal using different site symmetry point groups and also without use of the point symmetry at all. The site symmetry method allows one to predict the real symmetry of the defective crystal. This is demonstrated in the calculations of Cu impurity in LiCl crystal (the cubic symmetry of the perfect crystal is maintained for defective crystal), Fe impurity in SrTiO3 crystal (the point defect lowers the symmetry from cubic to tetragonal) and interstitial iodine atom in CsPbI3 crystal (the experimentally found I_2^- dumbell structure is confirmed only in the calculations without point symmetry restriction).

Giant thermal conductivity in diamane and the influence of horizontal reflection symmetry on phonon scattering

Diamane exhibits giant thermal conductivity and a horizontal reflection symmetry restriction on the phonon scattering phase space.

Neutrophil Leukocyte: Combustive Microbicidal Action and Chemiluminescence

Neutrophil leukocytes protect against a varied and complex array of microbes by providing microbicidal action that is simple, potent, and focused. Neutrophils provide such action via redox reactions that change the frontier orbitals of oxygen (O2) facilitating combustion. The spin conservation rules define the symmetry barrier that prevents direct reaction of diradical O2with nonradical molecules, explaining why combustion is not spontaneous. In burning, the spin barrier is overcome when energy causes homolytic bond cleavage producing radicals capable of reacting with diradical O2to yield oxygenated radical products that further participate in reactive propagation. Neutrophil mediated combustion is by a different pathway. Changing the spin quantum state of O2removes the symmetry restriction to reaction. Electronically excited singlet molecular oxygen (O2*1) is a potent electrophilic reactant with a finite lifetime that restricts its radius of reactivity and focuses combustive action on the target microbe. The resulting exergonic dioxygenation reactions produce electronically excited carbonyls that relax by light emission, that is, chemiluminescence. This overview of neutrophil combustive microbicidal action takes the perspectives of spin conservation and bosonic-fermionic frontier orbital considerations. The necessary principles of particle physics and quantum mechanics are developed and integrated into a fundamental explanation of neutrophil microbicidal metabolism.

Synthesis, Crystal Structure, and Infrared Spectroscopy of a novel hydronium trihydrate hybrid compound: (C6H22N4)2H9O4CdCl6CdCl5Cl2

A 0-dimensional (0D) hybrid compound, (C6H22N4)2H9O4CdCl6CdCl5Cl2 has been prepared by a facile conventional evaporation method. The crystal packing of discrete constituents of [Cd(1)Cl6] octahedra, [Cd(2)Cl5] trigonal bipyramids, Cl– ions, protonated tris(2-aminoethyl)amine molecules ([(C2H7N)3NH]4+) and H9O4+ ions, is stabilized by diverse hydrogen bonds of N-H···Cl, C-H···Cl and C-H···O. Uncommonly, an isolated chlorine ion (i.e. Cl(4)) is fixed at a special position at 12c(3.) by hydrogen bonds from four surrounding hydrogen atoms at a trigonal pyramidal configuration whereas other chlorine atoms Cl(1), Cl(2) and Cl(3) are stabilized by hydrogen bonds from 2, 2 and 3 hydrogen atoms at bifurcated, linear and trigonal configurations, respectively. The ordered arrangement of [Cl(4) [Cl(4)···H4] trigonal pyramidal configuration upward or downward is responsible for the long c-axis of the title compound. Additionally, a H9O4+ ion is entangled with symmetry restriction and half occupancy. All these features of the title compound add our new knowledge about hydrogen bonds.

SMEPOC– a computer program for the automatic generation of trial structural models for inorganic compounds with symmetry restriction

A new structure modelling algorithm that can automatically generate trial structure models based on a prior knowledge of the unit-cell content and space-group information is proposed. It can enumerate all possible equivalent position combination (EPC) models and eliminate unreasonable ones with symmetry restriction. Unlike other methods, it does not require the internal molecular connectivity or coordination polyhedron information and is mostly suitable for modelling inorganic crystals with independent atoms. Therefore, these EPC models can be used as input to global optimization procedures for inorganic crystal structure determination using powder diffraction data by the direct-space method. The efficiency of the direct-space method can be greatly improved using this EPC method because the global optimization problem in a 3N-parameter space can be divided into a set of simpler ones. A program,SMEPOC, that can generate all possible EPC models for further global optimization procedures has been developed and is now available from the authors upon request.

STATIC AND DYNAMIC NON-AXIAL OCTUPOLE DEFORMATIONS SUGGESTED BY SKYRME-HF AND SELFCONSISTENT RPA CALCULATIONS

On the basis of the symmetry-unrestricted, cranked Skyrme-Hartree-Fock (SHF) calculations, we discuss superdeformed (SD) rotational bands in (1) the 40 Ca region along the N=Z line, and (2) neutron-rich Sulfur isotopes up to the neutron-drip line. The calculation was carried out with the use of the three-dimensional (3D) coordinate-mesh representation without imposing any symmetry restriction. Stability of the SD bands against exotic deformations breaking both reflection and axial symmetries were carefully examined. The analysis indicates possible appearance of negative-parity rotational bands associated with octupole shape vibrational excitations built on the SD yrast band. We then present results of selfconsistent RPA calculation for such a new type of collective vibrational modes. The selfconsistent RPA calculations based on the SD local minima obtained by the SHF calculation were carried out by means of the mixed representation on the 3D Cartesian mesh in a box.