A5002013025- High-pressure geophysics and materials
- Advanced Chemical Physics Studies
- Superconductivity in MgB2 and Alloys
- Boron and Carbon Nanomaterials Research
- Diamond and Carbon-based Materials Research
- ZnO doping and properties
- Physics of Superconductivity and Magnetism
- Electronic and Structural Properties of Oxides
- Machine Learning in Materials Science
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Thin-Film Transistor Technologies
- Quantum, superfluid, helium dynamics
- Rare-earth and actinide compounds
- Copper-based nanomaterials and applications
- Inorganic Fluorides and Related Compounds
- Astro and Planetary Science
- Semiconductor materials and interfaces
- Graphene research and applications
- Ammonia Synthesis and Nitrogen Reduction
- Magnetic Properties of Alloys
- Hydrogen Storage and Materials
- Quantum Dots Synthesis And Properties
- Nanowire Synthesis and Applications
- Metal and Thin Film Mechanics
Bruker (Switzerland)
2023
RIKEN Center for Emergent Matter Science
2021-2022
Sapienza University of Rome
2019-2022
University of Basel
2016-2019
Max Planck Institute of Microstructure Physics
2013-2016
Max Planck Society
2015
Université Claude Bernard Lyon 1
2011-2013
Centre National de la Recherche Scientifique
2011-2013
Institut Lumière Matière
2013
Laboratoire de physique de la matière condensée
2012
A comparison of DFT methods Density functional theory (DFT) is now routinely used for simulating material properties. Many software packages are available, which makes it challenging to know the best use a specific calculation. Lejaeghere et al. compared calculated values equation states 71 elemental crystals from 15 different widely codes employing 40 potentials (see Perspective by Skylaris). Although there were variations in values, most recent and converged toward single value, with...
Two hydrogen-rich materials, H$_3$S and LaH$_{10}$, synthesized at megabar pressures, have revolutionized the field of condensed matter physics providing first glimpse to solution hundred-year-old problem room temperature superconductivity. The mechanism underlying superconductivity in these exceptional compounds is conventional electron-phonon coupling. Here we describe recent advances experimental techniques, theory first-principles computational methods which made possible discoveries....
Through a systematic structural search we found an allotrope of carbon with Cmmm symmetry which predict to be more stable than graphite for pressures above 10 GPa. This material, refer as Z-carbon, is formed by pure sp(3) bonds and it provides explanation several features in experimental x-ray diffraction Raman spectra under pressure. The transition from Z-carbon can occur through simple sliding buckling graphene sheets. Our calculations that transparent wide band-gap semiconductor hardness...
We present state-of-the-art first-principles calculations of the electronic and optical properties silicon allotropes with interesting characteristics for applications in thin-film solar cells. These new phases consist distorted $s{p}^{3}$ networks have a lower formation energy than other experimentally produced phases. Some these structures turned out to quasidirect dipole-allowed band gaps range 0.8--1.5 eV, display absorption coefficients comparable those chalcopyrites used record
Reports on sulfur hydride attaining metallicity under pressure and exhibiting superconductivity at temperatures as high 200 K have spurred an intense search for another room-temperature superconductor among hydrogen-rich compounds. Recently, compressed phosphorus (phosphine) was reported to metallize pressures above 45 GPa, reaching a superconducting transition temperature (${T}_{c}$) of 100 GPa. However, neither the exact composition nor crystal structure phase been conclusively determined....
Due to its low atomic mass hydrogen is the most promising element search for high-temperature phononic superconductors. However, metallic phases of are only expected at extreme pressures (400 GPa or higher). The measurement a record superconducting critical temperature 190 K in hydrogen-sulfur compound 200 pressure[1], shows that metallization can be reached significantly lower pressure by inserting it matrix other elements. In this work we re-investigate phase diagram and properties H-S...
Using multiwavelets, we have obtained total energies and corresponding atomization for the GGA-PBE hybrid-PBE0 density functionals a test set of 211 molecules with an unprecedented guaranteed μHartree accuracy. These quasi-exact references allow us to quantify accuracy standard all-electron basis sets that are believed be highly accurate molecules, such as Gaussian-type orbitals (GTOs), numeric atom-centered (NAOs), full-potential augmented plane wave (APW) methods. We show NAOs able achieve...
We present an application of Eliashberg theory superconductivity to study a set novel superconducting systems with wide range structural and chemical properties. The includes three intercalated group-IV honeycomb layered structures, SH3 at 200 GPa (the superconductor the highest measured critical temperature), similar system SeH3 150 GPa, lithium doped mono-layer black phosphorus. theoretical approach we adopt is recently developed, fully ab initio that takes into account Coulomb interaction...
A systematic ab initio search for low enthalpy phases of disilane (Si_2H_6) at high pressures was performed based on the minima hopping method. We found a novel metallic phase with Cmcm symmetry, which is enthalpically more favorable than recently proposed structures up to 280 GPa, but revealing compositional instability below 190 GPa. The has moderate electron-phonon coupling yielding superconducting transition temperature T_c around 20 K 100 decreasing 13 220 These values are an order...
Among elemental compounds, the high-pressure superconducting phase diagram of phosphorus is one most complex. Resistivity measurements and $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ superconductivity calculations reported in this paper solve for first time open controversies on anomalous trends; forming a single, consistent scenario multiple metastable structures which coexist beyond...
In this work, we show that the same theoretical tools successfully explain other hydrides systems under pressure seem to be at odds with recently claimed conventional room temperature superconductivity of carbonaceous sulfur hydride. We support our conclusions I) absence a dominant low-enthalpy stoichiometry and crystal structure in ternary phase diagram. II) Only thermodynamics C-doping phases appears marginally competing enthalpy against H$_3$S. III) Accurate results transition given by ab...
To elucidate the geometric structure of putative room-temperature superconductor, carbonaceous sulfur hydride (C-S-H), at high pressure, we present results an extensive computational search bulk C-S-H 250 GPa. Using minima hopping prediction method coupled to GPU-accelerated sirius library, more than 17 000 local with different stoichiometries in large simulation cells were investigated. Only 24 are favorable against elemental decomposition, and all them carbon-doped...
The zinc blende (γ) phase of copper iodide holds the record hole conductivity for intrinsic transparent p-type semiconductors. In this work, we employ a high-throughput approach to systematically explore strategies enhancing γ-CuI further by impurity incorporation. Our objectives are not only find practical increase in CuI thin films, but also possibility ambivalent doping. total 64 chemical elements were investigated as possible substitutionals on either or iodine site. All chalcogen found...
We identify a class of novel low energy phases the hydrogen storage material ${\mathrm{LiAlH}}_{4}$ by using ab initio minima hopping crystal structure prediction method. These are, unlike previous predictions and known structures similar materials, characterized polymeric networks consisting Al atoms interlinked with H atoms. The most stable is layered ionic $P{2}_{1}/c$ symmetry, it has lower free than previously reported over wide range temperatures. Furthermore, we carry out x-ray...
We propose perovskite nitrides with magnetic rare-earth metals as novel materials a range of technological applications. These appear to be thermodynamically stable and, in spite possessing different crystal structures and atomic environments, they retain the moment corresponding elemental metal. find both semiconductors, wide moments some systems posses record high anisotropy energies. Further tuning electronic properties can also expected by doping other rare-earths or creating solid...
We present a theoretical investigation on the electron-phonon superconductivity of honeycomb $M{X}_{2}$ layered structures where $X$ is one element group IV (C, Si, or Ge) and $M$ an alkali alkaline-earth metal. Among studied compositions we predict ${T}_{\mathrm{C}}$ 7 K in ${\mathrm{RbGe}}_{2}$, 9 ${\mathrm{RbSi}}_{2}$, 11 ${\mathrm{SrC}}_{2}$. All these compounds feature strongly anisotropic superconducting gap. Our results show that despite different doping levels structural properties,...
We performed a systematic structural search of high-pressure carbon allotropes for unit cells containing from 6 to 24 atoms using the minima hopping method. discovered series new structures that are consistently lower in enthalpy than ones previously reported. Most these include ($5+7$)- or ($4+8$)-membered rings and can therefore be placed families proposed by H. Niu et al. [Phys. Rev. Lett. 108, 135501 (2012)]. However, we also found three more with competitive enthalpies contain...
The application of pressure allows systematic tuning the charge density a material cleanly, that is, without changes to chemical composition via dopants, and exploratory high-pressure experiments can inform design bulk syntheses materials benefit from their properties under compression. electronic structural response semiconducting tin nitride Sn
Raman spectroscopy is a powerful tool to study the intrinsic vibrational characteristics of crystals, and, therefore, it an adequate technique explore phase transitions carbon under pressure. However, diamond-anvil cell, which used in experiments apply pressure, appears as broad intense feature spectra. This lies, unfortunately, same range principal modes recently proposed $s{p}^{3}$ structures. As these are hard distinguish from diamond cell background, we analyze all Raman-active present...
Performing high accuracy hybrid functional calculations for condensed matter systems containing a large number of atoms is at present computationally very demanding or even out reach if quality basis sets are used. We highly optimized multiple graphics processing unit implementation the exact exchange operator which allows one to perform fast density-functional theory (DFT) with systematic without additional approximations up thousand atoms. With this method DFT become accessible on...
We investigate the possibility of achieving high-temperature superconductivity in hydrides under pressure by inducing metallization otherwise insulating phases through doping, a path previously used to render standard semiconductors superconducting at ambient pressure. Following this idea, we study H
We present a methodology to predict magnetic systems using ab initio methods. By employing crystal structure method and spin-polarized calculations, we explore the relation between crystalline structures their properties. In this work, testbed cases of transition metal alloys (FeCr, FeMn, FeCo FeNi) are study in ferromagnetic case. find soft-magnetic properties for FeCr, FeMn while FeNi hard-magnetic predicted. particular, family FeNi, candidate with energy lower than tetrataenite was found....