Band-structure trend in hole-doped cuprates and correlation with Tcmax

By calculation and analysis of the bare conduction bands in a large number of hole-doped high-temperature superconductors, we have identified the energy of the so-called axial-orbital as the essential, material-dependent parameter. It is uniquely related to the range of the intra-layer hopping. It controls the Cu 4s-character, influences the perpendicular hopping, and correlates with the observed Tc at optimal doping. We explain its dependence on chemical composition and structure, and present a generic tight-binding model.Comment: 5 pages, Latex, 5 eps figure

Relaxation Effects in the Transition Temperature of Superconducting HgBa2CuO4+delta

In previous studies on a number of under- and overdoped high temperature superconductors, including YBa_{2}Cu_{3}O_{7-y} and Tl_{2}Ba_{2}CuO_{6+\delta}, the transition temperature T_c has been found to change with time in a manner which depends on the sample's detailed temperature and pressure history. This relaxation behavior in T_c is believed to originate from rearrangements within the oxygen sublattice. In the present high-pressure studies on HgBa_{2}CuO_{4+\delta} to 0.8 GPa we find clear evidence for weak relaxation effects in strongly under- and overdoped samples ($T_c\simeq 40 - 50 K$) with an activation energy $E_{A}(1 bar) \simeq 0.8 - 0.9 eV$. For overdoped HgBa_{2}CuO_{4+\delta} E_{A} increases under pressure more rapidly than previously observed for YBa_{2}Cu_{3}O_{6.41}, yielding an activation volume of +11 \pm 5 cm^{3}; the dependence of T_c on pressure is markedly nonlinear, an anomalous result for high-T_c superconductors in the present pressure range, giving evidence for a change in the electronic and/or structural properties near 0.4 GPa

The role of dynamical polarization of the ligand to metal charge transfer excitations in {\em ab initio} determination of effective exchange parameters

The role of the bridging ligand on the effective Heisenberg coupling parameters is analyzed in detail. This analysis strongly suggests that the ligand-to-metal charge transfer excitations are responsible for a large part of the final value of the magnetic coupling constant. This permits to suggest a new variant of the Difference Dedicated Configuration Interaction (DDCI) method, presently one of the most accurate and reliable for the evaluation of magnetic effective interactions. This new method treats the bridging ligand orbitals mediating the interaction at the same level than the magnetic orbitals and preserves the high quality of the DDCI results while being much less computationally demanding. The numerical accuracy of the new approach is illustrated on various systems with one or two magnetic electrons per magnetic center. The fact that accurate results can be obtained using a rather reduced configuration interaction space opens the possibility to study more complex systems with many magnetic centers and/or many electrons per center.Comment: 7 pages, 4 figure

RESEARCH OF MECHANICAL PROPERTIES OF AN EXPLOSIVE WITHIN A TEMPERATURE RANGE FROM 20 TO 100 °С

Взрывчатое вещество (ВВ) представляет собой спрессованную структуру, состоящую из гранул взрывчатки, армирующих волокон и связующего компонента. ВВ, как конструкционный материал, имеет различные диаграммы деформирования при растяжении и сжатии. В РФЯЦ-ВНИИТФ проведены испытания дух типов образцов из ВВ: полусферические образцы, нагруженные внутренним давлением, и цилиндрические образцы в условиях одноосного сжатия. Испытания проведены при температурах 20, 60, 80 и 100 °С. По результатам испытаний определены диаграммы деформирования ВВ в температурном диапазоне от +20 до +100 °С.The explosive is а pressed substance consists of an explosive granules, reinforcing fibers and a binder. The explosive as a structural material has different curves of deformation under tension and compression. In RFNC-VNIITF, tests were held for two types of the explosive: hemispherical samples loaded by internal pressure and cylindrical samples in uniaxial compression. Tests were held at temperatures of 20, 60, 80 and 100 °С. According to results of experiments the deformation curves of explosive were obtained within a temperature range from 20 to 100 °С

JUSTIFICATION OF THE MODEL STRENGTH OF THE HAND PNEUMATIC TRENCH-MORTAR IN STATIC AND DINAMIC LOADING

В настоящее время в РФЯЦ-ВНИИТФ проводится разработка ручного пневматического миномета (РПМ), в котором запуск мины происходит при по-мощи сжатого воздуха без использования взрывчатых веществ и порохов. Для проведения предварительной экспериментальной отработки разработан макет миномета. Для снижения стоимости предварительной отработки в макете проведена замене легких алюминиевых материалов на сталь. В докладе представлены результаты расчетов на прочность корпуса макета миномета при статической нагрузке и ударном взаимодействии. Анализ НДС миномета проводился в двух пакетах программ (ПП): ЛОГОС-Прочность и аналогичного коммерческого продукта (КП).Nowadays developing of the hand pneumatic trench-mortar is carry out in RFNC-VNIITF and activation of mina occurs by compressed air without using of explosive or powder. The model of a trench-mortar has been developed for an experimental pretreatment. Light aluminium materials have been replaced to steel for reduction cost of pretreatment. The paper presents the results of calculation for the model strength of the trench-mortal during static load and impact interaction. Analysis of stress-strain state of the trench-mortal is made in two software package: LOGOS-strength and a similar commercial product