Search results for "init"
showing 10 items of 6629 documents
Analysis and approximation of one-dimensional scalar conservation laws with general point constraints on the flux
2016
We introduce and analyze a class of models with nonlocal point constraints for traffic flow through bottlenecks, such as exits in the context of pedestrians traffic and reduction of lanes on a road under construction in vehicular traffic. Constraints are defined based on data collected from non-local in space and/or in time observations of the flow. We propose a theoretical analysis and discretization framework that permits to include different data acquisition strategies; a numerical comparison is provided. Nonlocal constraint allows to model, e.g., the irrational behavior (" panic ") near the exit observed in dense crowds and the capacity drop at tollbooth in vehicular traffic. Existence …
Cryptocurrencies in the Light of Money Definitions
2020
Purpose: The aim of the article is to attempt to assess the phenomenon of digital currencies through the prism of existing money definitions as well as to determine to what extent the existing definitions of money are able to answer the question whether private decentralized digital currencies are money in the traditional sense or are they a completely new phenomenon that cannot be put in the framework of previous definitions of money. Design/methodology/approach: This study provides a critical literature review of the cryptocurrency’s definitions in comparison to traditional money definition. The literature review was intended to determine whether bitcoin could be treated as money. Finding…
Comparative ab initio calculations of SrTiO3 and CaTiO3 polar (111) surfaces
2012
We present the results of calculations of SrTiO3 and CaTiO3 polar (111) surface relaxations, rumplings, energetics, optical band gaps, and charge distributions using the ab initio code CRYSTAL and a hybrid description of exchange and correlation. We have calculated the surface relaxation of the two possible terminations (Ti and SrO3 or CaO3) of the SrTiO3 and CaTiO3 (111) surfaces. According to our calculations, atoms of the first surface layer relax inwards for Ti-, SrO3-, and CaO3-terminated (111) surfaces of both materials. The only exception is outward relaxation of the SrO3-terminated SrTiO3 (111) surface upper layer Sr atom. For both Ti-terminated SrTiO3 and CaTiO3 (111) surfaces our …
Ab initiocalculations of theHcenters in MgF2crystals
2012
MgF2 with rutile structure is important wide-gap optical material with numerous applications. We present and discuss the results of calculations for basic hole defects - interstitial F atoms (called also the colour H centres). This study is based on the large scale ab initio DFT calculations using hybrid B3PW exchange-correlation functional as implemented into CRYSTAL computer code. The electronic structure, atomic geometry, charge density distribution are calculated and discussed.
Ab initio modeling of radiation damage in MgF2 crystals
2014
Abstract MgF2 with a rutile structure is important radiation-resistant material with numerous applications due to its transparency from vacuum ultraviolet to infrared range of photon energies. We present and discuss the results of calculations for basic radiation defects in this crystal. The study is based on the large scale ab initio DFT calculations using hybrid B3PW exchange–correlation functional and atomic basis set. We analyzed the electronic structure, atomic displacements, charge density distribution as well as defect formation energies using large supercells. We compared properties of close and well separated F−H (Frenkel) defect pairs as well as individual defects. We simulated al…
Ab initio structural and electronic band-structure study of MgSe
2015
We present a careful and detailed ab initio study of the crystal structure and electronic band structure of different crystalline phases of MgSe. Calculations were performed using the full-potential linear augmented plane wave method. To determine the crystal phase of the ground state of MgSe, we computed the total energy as a function of volume for the rock-salt, zinc-blende, wurtzite, and NiAs phases. From the optimized volume, and by using the Birch–Murnaghan equation of state the lattice parameters , the bulk moduli, and its first pressure derivative () for the different phases of MgSe were found. In our calculations, we have used the local density approach for the exchange–correlation …
Ab initio calculations of SrTiO3, BaTiO3, PbTiO3, CaTiO3, SrZrO3, PbZrO3 and BaZrO3 (001), (011) and (111) surfaces as well as F centers, polarons, K…
2014
In this paper, the review of recent results of calculations of surface relaxations, energetics, and bonding properties for ABO 3 perovskite (001), (011) and (111) surfaces using mostly a hybrid description of exchange and correlation is presented. Both AO and BO 2-terminations of the nonpolar (001) surface and A , BO , and O terminations of the polar (011) surface, as well as B and AO 3-terminations of the polar (111) surface were considered. On the AO -terminated (001) surface, all upper-layer A atoms relax inwards, while all second layer atoms relax outwards. For the BO 2-terminated (001) surface, in most cases, the largest relaxations are on the second-layer metal atoms. For almost all …
First‐principles modeling of the H color centers in MgF 2 crystals
2012
MgF2 with a rutile structure is important wide-gap optical material with numerous applications. We present and discuss the results of calculations for basic hole defects – interstitial F atoms (called also the colour H centers). This study is based on the large scale ab initio DFT calculations using hybrid B3PW exchange-correlation functional as implemented into CRYSTAL computer code. The electronic structure, atomic geometry, charge density distribution are calculated and compared with similar defects in CaF2 fluorite. It is shown that the H centers oriented nearly parallel to the (110) axis are energetically more favourable than those oriented along the (001) axis, in agreement with exper…
First-principles calculations of the atomic and electronic structure of SrZrO3 and PbZrO3 (001) and (011) surfaces.
2010
We present the results of calculations of surface relaxations, rumplings, energetics, optical band gaps, and charge distribution for the SrZrO(3) and PbZrO(3) (001) and (011) surfaces using the ab initio code CRYSTAL and a hybrid description of exchange and correlation. We consider both SrO(PbO) and ZrO(2) terminations of the (001) surface and Sr(Pb), ZrO, and O terminations of the polar SrZrO(3) and PbZrO(3) (011) surfaces. On the (001) surfaces, we find that all upper and third layer atoms relax inward, while outward relaxations of all atoms in the second layer are found with the sole exception of the SrO-terminated SrZrO(3) (001) surface second layer O atom. Between all (001) and (011) s…
The Effect of Oxygen Vacancies on the Atomic and Electronic Structure of Cubic ABO3Perovskite Bulk and the (001) Surface:Abinitio Calculations
2009
We employed the hybrid DFT-LCAO and GGA-PW approaches as implemented in the CRYSTAL and VASP codes, respectively, for large supercell calculations of neutral O vacancies with trapped electrons (known as F centers) in the bulk and on the (001) surface of three cubic perovskite crystals (SrTiO 3 , PbTiO 3 , and PbZrO 3 ). The local lattice relaxation, charge redistribution, and positions of defect energy levels within the band gap are compared for three perovskites under study. We demonstrate how the difference in chemical composition of host materials leads to quite different defect properties.