A5086574722- High-pressure geophysics and materials
- Rare-earth and actinide compounds
- Superconductivity in MgB2 and Alloys
- Hydrogen Storage and Materials
- Physics of Superconductivity and Magnetism
- Advanced Chemical Physics Studies
- Magnetic and transport properties of perovskites and related materials
- Boron and Carbon Nanomaterials Research
- Methane Hydrates and Related Phenomena
- Quantum, superfluid, helium dynamics
- Advanced Condensed Matter Physics
- Machine Learning in Materials Science
- Superconducting Materials and Applications
- Iron-based superconductors research
- Astro and Planetary Science
- Inorganic Fluorides and Related Compounds
- Solidification and crystal growth phenomena
- Nuclear Materials and Properties
- Crystal Structures and Properties
- Advanced Thermoelectric Materials and Devices
- Geochemistry and Geochronology of Asian Mineral Deposits
- Electron and X-Ray Spectroscopy Techniques
- Intermetallics and Advanced Alloy Properties
- Planetary Science and Exploration
- Gas Dynamics and Kinetic Theory
Sapienza University of Rome
2020-2024
TU Wien
2023-2024
Graz University of Technology
2019-2023
Nawi Graz
2020
In the last five years a large number of new high-temperature superconductors have been predicted and experimentally discovered among hydrogen-rich crystals, at pressures which are way too high to meet any practical application. this work, we report computational prediction hydride superconductor, LaBH$_{8}$, with T$_{c}$ 126 K pressure 50 GPa, thermodynamically stable above 100 dynamically down 40 an unprecedentedly low for high-T$_{c}$ hydrides. LaBH$_{8}$ can be seen as ternary...
Motivated by the recent report of room-temperature superconductivity at near-ambient pressure in N-doped lutetium hydride, we performed a comprehensive, detailed study phase diagram Lu-N-H system, looking for superconducting phases. We combined ab initio crystal structure prediction with ephemeral data-derived interatomic potentials to sample over 200,000 different structures. Out more than 150 structures predicted be metastable within ~50 meV from convex hull identify 52 viable candidates...
We report ab-initio calculations of the superconducting properties two high-Tc sodalite-like clathrate yttrium hydrides, YH6 and YH10, within fully anisotropic ME theory, including Coulomb corrections. For both compounds we find almost isotropic gaps, resulting from a uniform distribution electron-phonon coupling over phonon modes electronic states mixed Y H character. The screening is rather weak, in Morel-Anderson pseudopotential mu*= 0:11, at odds with claims unusually large Tc lanthanum...
Abstract We report the theoretical prediction of two high-performing hydride superconductors BaSiH 8 and SrSiH . They are thermodynamically stable above pressures 130 174 GPa, respectively, metastable below that. Employing anharmonic phonon calculations, we determine minimum dynamical stability to be around 3 GPa for 27 , using fully anisotropic Migdal-Eliashberg theory, predict T c ’s 71 126 K, respectively. also introduce a method estimate lowest pressure synthesis, based on calculation...
Abstract Motivated by the recent claim of hot superconductivity with critical temperatures up to 550 K in La + x hydrides, we investigate high-pressure phase diagram compounds that may have formed experiment, using first-principles calculations for evolutionary crystal structure prediction and superconductivity. Starting from hypothesis observed T c be realized successive heating upon a pre-formed LaH 10 phase, examine plausible ternaries lanthanum, hydrogen other elements present diamond...
We report a high-throughput ab-initio study of the thermodynamic and superconducting proper- ties recently synthesized XB$_3$C$_3$ clathrates. These compounds, in which boron carbon form sponge-like network interconnected cages each enclosing central X atom, are attractive candidates to achieve high-Tc conventional superconductivity at ambient pressure, due simultaneous presence stiff B-C covalent tunable charge reservoir, provided by guest atom. Ternary compounds like CaB$_3$C$_3$,...
The extreme pressures required to stabilize the recently discovered superhydrides represent a major obstacle their practical application. In this paper, we propose novel route attain high-temperature superconductivity in hydrides at ambient pressure, by doping commercial metal borohydrides. Using first-principles calculations based on Density Functional Theory and Migdal-Eliashberg theory, demonstrate that Ca(BH$_4$)$_2$ moderate hole of 0.03 holes per formula unit, obtained through partial...
Abstract High-temperature unconventional superconductivity quite generically emerges from doping a strongly correlated parent compound, often (close to) an antiferromagnetic insulator. The recently developed dynamical vertex approximation is state-of-the-art technique that has quantitatively predicted the superconducting dome of nickelates. Here, we apply it to study effect pressure in infinite-layer nickelate Sr x Pr 1− NiO 2 . We reproduce increase critical temperature ( T c ) under found...
Motivated by the recent discovery of near-room temperature superconductivity in high-pressure superhydrides, we investigate from first principles superconducting phase diagram ternary Ca-B-H system, using ab initio evolutionary crystal structure prediction, and Density Functional Perturbation Theory. We find that below 100 GPa all stable weakly metastable phases are insulating. This pressure marks appearance several new chemically-forbidden on hull stability, onset metalization...
The quantum nature of the hydrogen lattice in superconducting hydrides can have crucial effects on material's properties. Taking a detailed look at dynamic stability recently predicted BaSiH
We briefly review the status quo of research on putative superconductor Pb9Cu(PO4)6O also known as LK-99. Further, we provideab initioderived tight-binding parameters for a two- and five-band model, solve these in dynamical-mean-field theory. The interaction-to-bandwidth ratio makes LK-99 Mott or charge transfer insulator. Electron hole doping (which is different from substituting Pb by Cu thus differs LK-99) required to make it metallic potentially superconducting.
Traditional thermoelectric materials rely on low thermal conductivity to enhance their efficiency but suffer from inherently limited power factors. Novel pathways optimize electronic transport are thus crucial. Here, we achieve ultrahigh factors in Ni$_3$Ge through a new design principle. When overlapping flat and dispersive bands engineered the Fermi level, charge carriers can undergo intense interband scattering, yielding an energy filtering effect similar what has long been predicted...
Following the successful prediction of superconducting phase diagram for infinite-layer nickelates, here we calculate $T_{\mathrm{c}}$ vs. number layers $n$ finite-layer nickelates using dynamical vertex approximation. To this end, start with density functional theory, and include local correlations non-perturbatively by mean-field theory $n=2$ to 7. For all $n$, Ni $d_{x^2-y^2}$ orbital crosses Fermi level, but $n>4$ there are additional $(\pi, \pi)$ pockets or tubes that slightly enhance...
The discovery of high-${T}_{c}$ conventional superconductivity in high-pressure hydrides has helped establish computational methods as a formidable tool to guide material discoveries field traditionally dominated by serendipitous experimental search. This paves the way an ever-increasing use data-driven approaches study and design superconductors. In this work, we propose new adaptive method generate meaningful datasets superconductors, based on element substitution into small set...
A recent experiment [X. Ding et al., Nature (London) 615, 50 (2023)] indicates that superconductivity in nickelates is restricted to a narrow window of hydrogen concentration, $0.22<x<0.28$ ${\mathrm{Nd}}_{0.8}{\mathrm{Sr}}_{0.2}{\mathrm{NiO}}_{2}{\mathrm{H}}_{x}$. This reported necessity suggests it plays crucial role for superconductivity, as does the vast field hydride superconductors. Using density-functional theory and its extensions, we explore effect topotactic on electronic structure...
We briefly review the status quo of research on putative superconductor Pb$_9$Cu(PO$_4$)$_6$O also known as LK-99. Further, we provide {\em ab initio} derived tight-binding parameters for a two- and five-band model, solve these in dynamical-mean-field theory. The ratio interaction-to-bandwidth makes LK-99 Mott or charge transfer insulator. Electron hole doping (which is different from substituting Pb by Cu thus differs LK-99) required to make it metallic potentially superconducting.
In this work we probe the possibility of high-temperature conventional superconductivity in boron-carbon system, using ab-initio screening. A database 320 metastable structures with fixed composition (50$\%$/50$\%$) is generated Minima-Hopping method, and characterized electronic vibrational descriptors. Full electron-phonon calculations on sixteen representative allow to identify general trends $T_{\textrm{c}}$ across within four families energy landscape, construct an approximate...
By means of $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations, the authors show here that neither a conventional nor an unconventional pairing mechanism can justify observed 26-K superconducting ${T}_{c}$ in compressed bcc titanium. They reconcile experimental and theoretical results by assuming presence Ti vacancies. These induce phonon softening increases electron-phonon...
We present the first $ab$-$initio$ study of superconductivity in NbTi, workhorse for many applications. Despite its apparent simplicity, NbTi turns out to be a major challenge computational superconductivity. In fact, anharmonic effects are crucial obtain dynamically stable phonons ordered bcc phase, unstable at harmonic level, and beyond-Morel Anderson Coulomb interaction reduce Tc by more than 20%. Lattice disorder causes an additional large discrepancy $T_c$ compared experiment. Our...
Conflicting theoretical scenarios for infinite-layer nickelate superconductors have been hotly debated, particularly regarding whether only a single Ni-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>3</a:mn><a:msub><a:mi>d</a:mi><a:mrow><a:msup><a:mi>x</a:mi><a:mn>2</a:mn></a:msup><a:mo>−</a:mo><a:msup><a:mi>y</a:mi><a:mn>2</a:mn></a:msup></a:mrow></a:msub></a:mrow></a:math> band is relevant at low energies besides electron pockets or multiorbital physics including...
Abstract This paper introduces the HEX (High-pressure Elemental Xstals) database, a complete database of ground-state crystal structures first 57 elements periodic table, from H to La, at 0, 100, 200 and 300 GPa. aims provide unified reference for high-pressure research, by compiling all available experimental information on high pressure, complementing it with results accurate evolutionary structure prediction runs based Density Functional Theory. Besides offering much-needed reference, our...
Hydrogen hydrates are among the basic constituents of our solar system’s outer planets, some their moons, as well Neptune-like exo-planets. The details high-pressure phases and thermodynamic conditions formation stability fundamental information for establishing presence hydrogen in interior those celestial bodies, example, against pure components (water ice molecular hydrogen). Here, we report a synthesis path experimental observation, by X-ray diffraction Raman spectroscopy measurements,...
A recent experiment [X. Ding et al., Nature 615, 50 (2023)] indicates that superconductivity in nickelates is restricted to a narrow window of hydrogen concentration: 0.22 < x 0.28 Nd$_{0.8}$Sr$_{0.2}$NiO$_{2}$H$_{x}$. This reported necessity suggests it plays crucial role for superconductivity, as does the vast field hydride superconductors. Using density-functional theory and its extensions, we explore effect topotactic on electronic structure phonon-mediated nickelate Our calculations...