The spin angular gradient approximation in the density functional theory

A spin angular gradient approximation for the exchange correlation magnetic field in the density functional formalism is proposed. The usage of such corrections leads to a consistent spin dynamical approach beyond the local approximation. The proposed technique does not contain any approximations for the form of potential and can be used in modern full potential band structure methods. The obtained results indicate that the direct 'potential' exchange in 3d magnets is rather small compared to the indirect 'kinetic' exchange, thus justifies the dynamical aspect of the local density approximation in 3d metals

Electronic Structure and Magnetic Properties of Solids

We review basic computational techniques for simulations of various magnetic properties of solids. Several applications to compute magnetic anisotropy energy, spin wave spectra, magnetic susceptibilities and temperature dependent magnetisations for a number of real systems are presented for illustrative purposes.Comment: Review article; To appear in Journal of Computational Crystallograph

Electron energy spectrum and magnetic interactions in high-T(sub c) superconductors

The character of magnetic interactions in La-Sr-Cu-O and Y-Ba-Cu-O systems is of primary importance for analysis of high-T(sub c) superconductivity in these compounds. Neutron diffraction experiments showed the antiferromagnetic ground state for nonsuperconducting La2CuO4 and YBa2Cu3O6 with the strongest antiferromagnetic superexchange being in the ab plane. The nonsuperconducting '1-2-3' system has two Neel temperatures T sub N1 and T sub N2. The first one corresponds to the ordering of Cu atoms in the CuO2 planes; T sub N2 reflects the antiferromagnetic ordering of magnetic moments in CuO chains relatively to the moments in the planes T sub N1 and T sub N2 depend strongly on the oxygen content. Researchers describe magnetic interactions in high-T superconductors based on the Linear Muffin-Tin Orbitals (LMTO) band structure calculations. Exchange interaction parameters can be defined from the effective Heisenberg hamiltonian. When the magnetic moments are not too large, as copper magnetic moments in superconducting oxides, J sub ij parameters can be defined through the non-local magnetic susceptibility of spin restricted solution for the crystal. The results of nonlocal magnetic susceptibility calculations and the values of exchange interaction parameters for La CuO and YBa2Cu3O7 systems are given in tabular form. Strong anisotropy of exchange interactions in the ab plane and along the c axis in La2CuO4 is obviously seen. The value of Neel temperature found agrees well with the experimental data available. In the planes of '1-2-3' system there are quite strong antiferromagnetic Cu-O and O-O interaction which appear due to holes in oxygen subbands. These results are in line with the magnetic model of oxygen holes pairing in high-T(sub c) superconductors

Cycle of the needs satisfaction, and information support of the society development simulation system

The report focuses on some of the key points of constructing a model of an artificial society. It is based on the processes of emergence and implementation of the needs of specific agents, depending on the internal processes in the agents, and external environmental factors. Unlike in other approaches, the basis of the modeled system agents' behavior is the concept of needs as the necessity of implementation of the agents' transition from one state to another. This article presents an algorithm of the needs satisfaction of the agent, starting with the event that caused the need for, and ending its satisfaction, or the message that it is impossible to satisfy. The basis of objective knowledge in the system are a model of active and passive agents, as well as recipes meet the needs of the active agents and the relationships between them. © 2017 Author(s)

Spin wave dispersion based on the quasiparticle self-consistent GWGW method: NiO, MnO and α\alpha-MnAs

We present spin wave dispersions in MnO, NiO, and $\alpha$-MnAs based on the quasiparticle self-consistent $GW$ method (\qsgw), which determines an optimum quasiparticle picture. For MnO and NiO, \qsgw results are in rather good agreement with experiments, in contrast to the LDA and LDA+U description. For $\alpha$-MnAs, we find a collinear ferromagnetic ground state in \qsgw, while this phase is unstable in the LDA.Comment: V2: add another figure for SW life time. Formalism is detaile

Spin-density fluctuations and the fluctuation-dissipation theorem in 3d ferromagnetic metals

Spatial and time scales of spin density fluctuations (SDF) were analyzed in 3d ferromagnets using ab initio linear response calculations of complete wavevector and energy dependence of the dynamic spin susceptibility tensor. We demonstrate that SDF are spread continuously over the entire Brillouin zone and while majority of them reside within the 3d bandwidth, a significant amount comes from much higher energies. A validity of the adiabatic approximation in spin dynamics is discussed. The SDF spectrum is shown to have two main constituents: a minor low-energy spin wave contribution and a much larger high-energy component from more localized excitations. Using the fluctuation-dissipation theorem (FDT), the on-site spin correlator (SC) and the related effective fluctuating moment were properly evaluated and their universal dependence on the 3d band population is further discussed

Land management cluster zonning’s methods summary

The article focuses on methods of land management cluster zoning analysis. The authors have analyzed a lot of articles and books about zoning and concluded that there was insufficient attention to zoning methods. The article goal is to study different methods of cluster zoning (clustering of the municipal districts of a Russian region) for purposes of land management information support. The authors have defined the concept of “land management cluster zoning”, have analyzed the tree model method, the integrated zoning method and zoning based on the criterion of the efficiency of land management. These methods allow for cluster zoning of municipal districts. These methods have been tested using data from Novgorod Region. Based on the results of the study the authors have concluded that various zoning methods have yielded results close to 80%, but the choice of method should take into account the zoning purposes. For example, the tree model method is the most suitable one in the case of zoning based on indicators that have identical impact on land management. The method of integrated zoning is the most appropriate for application in the case of indications having different impact on land management. Zoning based on the criterion of land management efficiency separates municipal districts by one indicator. But this indicator is the key one.Статья посвящена вопросам анализа методов проведения кластерного зонирования территория региона для целей управления земельными ресурсами. Авторы проанализировали имеющийся массив литературных источников по теме и сделали вывод о незначительном внимании, которое уделяется непосредственно методам зонирования. Целью статьи является исследование различных методов кластерного зонирования региона (кластеризации административных образований, входящих в субъект Федерации) для целей информационного обеспечения процесса стратегического управления земельными и природными ресурсами региона. Для достижения указанной цели было дано определение кластерного зонирования для целей управления земельными ресурсами, проанализированы методы древовидной модели, зонирования с помощью интегрального показателя и зонирования по показателю эффективности, позволяющие разделить провести кластерное зонирование муниципальных образований региона. С помощью указанных методов проведено зонирование территории Новгородской области. По результатам исследования сделаны выводы, что различные методы зонирования в 80 % дали схожие между собой результаты, но различия в основе каждого из трех рассматриваемых методов позволяют выработать рекомендации по их применению, исходя из целей зонирования. Например, метод древовидной модели наиболее целесообразно применять при наличии комплекса показателей, оказывающих одинаковое влияние на управление земельными ресурсами. Метод комплексного зонирования разумнее всего применять в случаях, когда значимость факторов, влияющих на систему управления земельными ресурсами, сильно различается. Метод зонирования по критерию экономической эффективности разделяет муниципальные образования по одному, но ключевому для системы управления земельными ресурсами показателю. Широкие возможности открываются для использования результатов кластерного зонирования в системе стратегического планирования использования земельных ресурсов на региональных и муниципальных уровнях, т. к. в результате применения кластерного зонирования образуются группы муниципальных образований, однородных по показателям, влияющим на использование земельных ресурсов, или однородных по качеству управления ими

Magnetic susceptibility, exchange interactions and spin-wave spectra in the local spin density approximation

Starting from exact expression for the dynamical spin susceptibility in the time-dependent density functional theory a controversial issue about exchange interaction parameters and spin-wave excitation spectra of itinerant electron ferromagnets is reconsidered. It is shown that the original expressions for exchange integrals based on the magnetic force theorem (J. Phys. F14 L125 (1984)) are optimal for the calculations of the magnon spectrum whereas static response function is better described by the ``renormalized'' magnetic force theorem by P. Bruno (Phys. Rev. Lett. 90, 087205 (2003)). This conclusion is confirmed by the {\it ab initio} calculations for Fe and Ni.Comment: 12 pages, 2 figures, submitted to JPC

Spin-polarized scanning tunneling microscopy of half-metallic ferromagnets: Non-quasiparticle contributions

The role of the many-body (spin-polaronic) effects in the scanning tunneling spectroscopy of half-metallic ferromagnets (HMF) is considered. It is shown that the non-quasiparticle (NQP) states exist in the majority or minority spin gap in the presence of arbitrary external potential and, in particular, at the surfaces and interfaces. Energy dependence of the NQP density of states is obtained in various models of HMF, an important role of the hybridization nature of the energy gap being demonstrated. The corresponding temperature dependence of spin polarization is calculated. It is shown that the NQP states result in a sharp bias dependence of the tunneling conductance near zero bias. Asymmetry of the NQP states with respect to the Fermi energy provides an opportunity to separate phonon and magnon peaks in the inelastic spectroscopy by STM.Comment: 13 pages, 6 figure