A5010870768- Rare-earth and actinide compounds
- Advanced Chemical Physics Studies
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Nuclear Materials and Properties
- Magnetic properties of thin films
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- High-pressure geophysics and materials
- Surface and Thin Film Phenomena
- Radioactive element chemistry and processing
- Advanced Condensed Matter Physics
- Magnetic Properties of Alloys
- Graphene research and applications
- Cold Atom Physics and Bose-Einstein Condensates
- Electronic and Structural Properties of Oxides
- X-ray Diffraction in Crystallography
- Catalysis and Oxidation Reactions
- X-ray Spectroscopy and Fluorescence Analysis
- Molecular Junctions and Nanostructures
- Thermodynamic and Structural Properties of Metals and Alloys
- Diamond and Carbon-based Materials Research
- Material Properties and Failure Mechanisms
- Spectroscopy and Quantum Chemical Studies
- Electron and X-Ray Spectroscopy Techniques
Czech Academy of Sciences, Institute of Physics
2015-2025
Czech Academy of Sciences
2014-2024
Czech Academy of Sciences, Institute of Plasma Physics
2006-2015
Universität Hamburg
2010-2012
North Carolina State University
2006-2011
Joint Research Centre
2011
The quantum Monte Carlo methods represent a powerful and broadly applicable computational tool for finding very accurate solutions of the stationary Schroedinger equation atoms, molecules, solids variety model systems. algorithms are intrinsically parallel able to take full advantage present-day high-performance computing This review article concentrates on fixed-node/fixed-phase diffusion method with emphasis its applications electronic structure other extended many-particle
We report a straightforward method to produce high-quality nitrogen-doped graphene on SiC(0001) using direct nitrogen ion implantation and subsequent stabilization at temperatures above 1300 K. demonstrate that double defects, which comprise two defects in second-nearest-neighbor (meta) configuration, can be formed controlled way by adjusting the duration of bombardment. Two types atomic contrast single N are identified scanning tunneling microscopy. attribute origin these contrasts...
A century on from its discovery, a complete fundamental understanding of superconductivity is still missing. Considerable research efforts are currently devoted to elucidating mechanisms by which pairs electrons can bind together through the mediation boson field different than one associated vibrations crystal lattice. PuCoGa_5, 5f-electron heavy-fermion superconductor with record critical temperature T_c=18.5 K, many compounds for short-range, isotropic attraction provided simple...
We determine the equation of state stoichiometric FeO by employing diffusion Monte Carlo method. The fermionic nodes are fixed a single Slater determinant spin-unrestricted orbitals. calculated ambient-pressure properties (lattice constant, bulk modulus, and cohesive energy) agree very well with available experimental data. At approximately 65 GPa, atomic lattice changes from rocksalt B1 to NiAs-type inverse B8 structure.
We investigate how the fixed-node diffusion Monte Carlo energy of solids depends on single-particle orbitals used in Slater-Jastrow wave functions. demonstrate that dependence can be significant, particular case $3d$ transition-metal compounds, which we adopt as examples. illustrate exchange-correlation functionals with variable exact-exchange component exploited to reduce errors. On basis these results argue quantum provides a variational approach for optimization effective Hamiltonians parameters.
The local-density approximation combined with the dynamical mean-field theory (LDA+DMFT) is applied to paramagnetic phase of light actinide dioxides: UO2, NpO2, and PuO2. calculated band gaps valence-band electronic structure are in a very good agreement optical absorption experiments as well photoemission spectra. hybridization 5f shell 2p states oxygen found be relatively large, it increases filling orbitals from nominal ionic configurations two, three, four electrons nearly half-integer...
We combine several numerical and semi-analytical methods to study the $5d$ double perovskites Sr2YIRO6 Ba2YIRO6 which were recently proposed exhibit excitonic magnetism. Starting from density functional theory constrained random phase approximation we construct effective multi-band Hubbard models. These are analyzed by means of static dynamical mean-field theories strong coupling expansion. find both materials be insulators, but, contrary experimental claims, with a large spin gap hundreds...
One-dimensional metal-organic chains often possess a complex magnetic structure susceptible to modification by alteration of their chemical composition. The possibility tune properties provides an interesting playground explore quasi-particle interactions in low-dimensional systems. Despite the great effort invested so far, detailed understanding governing electronic and systems is still incomplete. One reasons limited ability characterize at atomic scale. Here, we provide comprehensive...
The around-mean-field $\mathrm{LSDA}+\mathrm{U}$ correlated band theory is applied to investigate the electronic and magnetic structure of $\mathrm{fcc}\text{\ensuremath{-}}\mathrm{Pu}\text{\ensuremath{-}}\mathrm{Am}$ alloys. Despite a lattice expansion caused by Am atoms, neither tendency $5f$ localization nor formation local moments on Pu atoms in $\mathrm{Pu}\text{\ensuremath{-}}\mathrm{Am}$ alloys found. manifolds are calculated, being very similar simple weighted superposition elemental states.
We propose a straightforward and efficient procedure to perform dynamical mean-field (DMFT) calculations on the top of static LDA+U approximation. Starting from self-consistent ground state we included multiplet transitions using Hubbard-I approximation, which yields very good agreement with experimental photoelectron spectra δ-Pu, Am, their selected compounds.
The correlated band theory implemented as a combination of the local density approximation with exact diagonalization Anderson impurity model is applied to PuO$_2$. We obtain an insulating electronic structure consistent experimental photoemission spectra. calculations yield gap 1.8 eV and non-magnetic singlet ground state that characterized by non-integer filling plutonium $f$ shell ($n_f\approx 4.5$). Due sizeable hybridization $p$ states oxygen, more complex than four-electron...
Electronic structure calculations combining the local-density approximation with an exact diagonalization of Anderson impurity model show intermediate 5f^5-5f^6-valence ground state and delocalization 5f^5 multiplet Pu atom 5f-shell in PuCoIn_5, PuCoGa_5, \delta-Pu. The 5f-local magnetic moment is compensated by a formed surrounding cloud conduction electrons. For PuCoGa_5 \delta-Pu compensation complete singlet. PuCoIn_5 partial magnetic. We suggest that unconventional d-wave...
We report on the magnetic properties of Dy atoms adsorbed (001) surface SrTiO
We report the valence-to-core resonant inelastic x-ray scattering of EuS measured at L_{3} edge Eu. The obtained data reveal two sets excitations: one set is composed a hole in S 3p bands and an electron excited to extended Eu 5d band states, other made up from 4f states localized bound by its Coulomb potential. delocalized excitations arise dipole-allowed 5d→2p emissions, whereas result dipole-forbidden (quadrupole-allowed) 4f→2p emissions. Both these emission channels have comparable...
We provide a straightforward and numerically efficient procedure to perform local-density-$\text{approximation}+\text{Hubbard}$ I approximation $(\text{LDA}+\text{HIA})$ calculations, including self-consistency over the charge density, within full potential linearized augmented plane-wave (FP-LAPW) method. This implementation is all-electron, includes spin-orbit interaction, makes no shape approximations for density. The method applied calculate selected heavy actinides in paramagnetic...
The valence-band spectrum of the ferromagnetic nickel is calculated using LDA+DMFT method. auxiliary impurity model emerging in course calculations discretized and solved with exact diagonalization, or, more precisely, Lanczos Particular emphasis given to spin dependence satellite that observed around 6 eV below Fermi level. strongly polarized agreement experimental findings.
The electronic structure of selected rare-earth atoms adsorbed on a free-standing graphene was investigated using methods beyond the conventional density functional theory (DFT+U, DFT+HIA and DFT+ED). influence electron correlations spin-orbit coupling magnetic properties has been examined. DFT+U method predicts both to carry local moments (spin orbital) contrary nonmagnetic $f^6$ ($J=0$) ground-state configuration Sm in gas phase. Application DFT${}+{}$Hubbard-I (HIA) DFT${}+{}$exact...
Over the past two decades, continuum quantum Monte Carlo (QMC) has proved to be an invaluable tool for predicting of properties matter from fundamental principles. By solving Schrödinger equation through a stochastic projection, it achieves greatest accuracy and reliability methods available physical systems containing more than few particles. QMC enjoys scaling favorable chemical methods, with computational effort which grows second or third power system size. This scalability enabled...
We calculate the ground-state properties of an unpolarized two-component Fermi gas with aid diffusion quantum Monte Carlo (DMC) methods. Using extrapolation to zero effective range attractive two-particle interaction, we find $E/{E}_{\mathrm{free}}$ in unitary limit be 0.212(2), 0.407(2), 0.409(3), and 0.398(3) for 4, 14, 38, 66 atoms, respectively. Our calculations indicate that dependence total energy on interaction ${R}_{\mathrm{eff}}$ is sizable ${R}_{\mathrm{eff}}=0$ therefore important...
Understanding the electronic structure of materials containing elements from end periodic table represents a challenge due to complex interplay number physical phenomena occurring in these systems. In plutonium metal, fraction valence electrons is at turning point between joining conduction cloud, which occupies whole crystal, and staying bound particular atom. This delicate boundary can be probed by photoemission experiments. Here we employ very accurate computational method---the quantum...
Research Article| January 01, 2010 Quantum Monte Carlo Studies of Transition Metal Oxides Lubos Mitas; Mitas Center for High Performance Simulation and Department Physics North Carolina State University Raleigh, Carolina, 27695-8202 U.S.A., lmitas@ncsu.edu Search other works by this author on: GSW Google Scholar Jindřich Kolorenč Hamburg, Jungiusstrasse 9 20355 Germany, Institute Physics, ASCR, Na Slovance 2 CZ-18221 Prague, Czech Republic Author Article Information Publisher:...
We address a recent controversy concerning the magnetic state of holmium adatom on platinum surface. Within combination density functional theory (DFT) with exact diagonalization (ED) Anderson impurity model, 〈J z 〉 = 0 paramagnetic ground |J 8, J ±8〉 is found. In an external field, this transformed to spin-polarized ≈ 6.7. emphasize role 5d-4f interorbital exchange polarization in modification 4f shell energy spectrum.
The debate whether uranium $5f$ electrons are closer to being localized or itinerant in the ferromagnetic compound $\mathrm{U}{\mathrm{Ga}}_{2}$ is not yet fully settled. experimentally determined magnetic moments large, approximately $3\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$, suggesting character of electrons. In same time, one can identify signs as well behavior various spectroscopic observations. band theory, employing local exchange-correlation functionals, biased...