A5007613136- Advanced Chemical Physics Studies
- Graphene research and applications
- Thermal properties of materials
- High-pressure geophysics and materials
- Surface and Thin Film Phenomena
- X-ray Diffraction in Crystallography
- Rare-earth and actinide compounds
- Advanced Thermoelectric Materials and Devices
- Carbon Nanotubes in Composites
- Quantum and electron transport phenomena
- Crystallization and Solubility Studies
- Physics of Superconductivity and Magnetism
- Boron and Carbon Nanomaterials Research
- Electronic and Structural Properties of Oxides
- Catalytic Processes in Materials Science
- Quantum, superfluid, helium dynamics
- Diamond and Carbon-based Materials Research
- Cold Atom Physics and Bose-Einstein Condensates
- 2D Materials and Applications
- Superconductivity in MgB2 and Alloys
- Thermal Radiation and Cooling Technologies
- Machine Learning in Materials Science
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Thermodynamics and Statistical Mechanics
- Chalcogenide Semiconductor Thin Films
King's College London
2013-2023
University of Edinburgh
2020-2022
King's College School
2013
University of Oxford
2011-2012
Massachusetts Institute of Technology
2006-2011
Scuola Internazionale Superiore di Studi Avanzati
2003-2007
Jožef Stefan International Postgraduate School
2004-2006
Jožef Stefan Institute
2004-2006
AREA Science Park
2005
University of Milano-Bicocca
2001-2003
QUANTUM ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, pseudopotentials (norm-conserving, ultrasoft, projector-augmented wave). The acronym stands opEn Source Package Research in Electronic Structure, Simulation, Optimization. It freely available to researchers around the world under terms GNU General Public License. builds upon newly-restructured that have been developed tested...
We uncover the constitutive relation of graphene and probe physics its optical phonons by studying Raman spectrum as a function uniaxial strain. find that doubly degenerate ${E}_{2g}$ mode splits in two components: one polarized along strain other perpendicular. This $G$ peak into bands, which we call ${G}^{+}$ ${G}^{\ensuremath{-}}$, analogy with effect curvature on nanotube peak. Both peaks redshift increasing their splitting increases, excellent agreement first-principles calculations....
We determine the effect of defects induced by ion bombardment on Raman spectrum single-layer molybdenum disulfide. The evolution both linewidths and frequency shifts first-order bands with density is explained a phonon confinement model, using functional theory to calculate dispersion curves. identify several defect-induced scattering peaks arising from zone-edge modes. Among these, most prominent $\mathrm{LA}(M)$ peak at...
The thermal conductivity of disordered silicon-germanium alloys is computed from density-functional perturbation theory and with relaxation times that include both harmonic anharmonic scattering terms. We show this approach yields an excellent agreement at all compositions experimental results provides clear design rules for the engineering nanostructured thermoelectrics. For Si(x)Ge(1-x), more than 50% heat carried room temperature by phonons mean free path greater 1 μm, addition as little...
We determine from first principles the finite-temperature properties-linewidths, line shifts, and lifetimes-of key vibrational modes that dominate inelastic losses in graphitic materials. In graphite, phonon linewidth of Raman-active E(2g) mode is found to decrease with temperature; such anomalous behavior driven entirely by electron-phonon interactions, does not appear nearly degenerate infrared-active E(1u) mode. graphene, anharmonic lifetimes decay channels A(1)' at K over Gamma couple...
Abstract EPW is an open-source software for ab initio calculations of electron–phonon interactions and related materials properties. The code combines density functional perturbation theory maximally localized Wannier functions to efficiently compute coupling matrix elements, perform predictive temperature-dependent properties phonon-assisted quantum processes in bulk solids low-dimensional materials. Here, we report on significant developments the since 2016, namely: a transport module...
We use first-principles methods based on density functional perturbation theory to characterize the lifetimes of acoustic phonon modes and their consequences thermal transport properties graphene. show that using a standard perturbative approach, transverse longitudinal phonons in free-standing graphene display finite long-wavelength limit, making them ill-defined as elementary excitations samples dimensions larger than ∼1 μm. This behavior is entirely due presence quadratic dispersions for...
Electron-phonon coupling in graphene is extensively modeled and simulated from first principles. We find that using an accurate model for the polarizations of acoustic phonon modes crucial to obtain correct numerical results. The interactions between electrons modes, gauge field deformation potential, are calculated at DFT level framework linear response. zero-momentum limit phonons interpreted as a strain pattern, allowing calculation parameter GW approximation. role electronic screening on...
We present a first-principles computational approach to calculate thermoelectric transport coefficients via the exact solution of linearized Boltzmann equation, also including effect nonequilibrium phonon populations induced by temperature gradient. use density functional theory and perturbation for an accurate description electronic vibrational properties system, electron-phonon interactions; carriers' scattering rates are computed using standard theory. exploit Wannier interpolation (both...
Significant progress on parameter-free calculations of carrier mobilities in real materials has been made during the past decade; however, role various approximations remains unclear and a unified methodology is lacking. Here, we present analyse comprehensive efficient approach to compute intrinsic, phonon-limited drift Hall semiconductors, within framework first-principles Boltzmann transport equation. The exploits novel for estimating quadrupole tensors including them electron-phonon...
The thermal conductivity of ideal short-period superlattices is computed using harmonic and anharmonic force constants derived from density-functional perturbation theory by solving the Boltzmann transport equation in single-mode relaxation time approximation, silicon–germanium as a paradigmatic case. We show that limit small superlattice period can exceed both constituent materials. This found to be due dramatic reduction scattering acoustic phonons optical phonons, leading very long phonon...
We present a first-principles study of the temperature- and density-dependent intrinsic electrical resistivity graphene. use density-functional theory perturbation together with very accurate Wannier interpolations to compute all electronic vibrational properties electron-phonon coupling matrix elements; phonon-limited is then calculated within Boltzmann-transport approach. An effective tight-binding model, validated against results, also used role electron-electron interactions at level...
Enhanced thermoelectric performance of Cu<sub>3</sub>SbS<sub>4</sub> with fine microstructure and optimized carrier concentration by Sn-doping.
Cu3SbS4 is a copper-based sulfide composed of earth-abundant elements. We present combined theoretical and experimental study the thermoelectric properties Ge-doped Cu3SbS4. On basis density functional theory, we found that pristine compound semiconductor with large density-of-state effective mass ∼2.2 me for holes. Ge was predicted to be an p-type dopant only slightly shifts band structure The power factor reach maximum value 10–15 mol % Ge-doping on Sb site (n = (6–9) × 1020 cm–3) at high...
The first two steps of methane dissociation on Rh(111) have been investigated using density-functional theory, focusing the dependence catalyst's reactivity atomic coordination active metal site. We find that, although barrier for dehydrogenation (CH4 --> CH3 + H) decreases as expected with binding site, methyl (CH3 CH2 is hindered at an ad-atom defect, where reaction instead most favored. Our findings indicate if it were possible to let occur selectively defects, could be blocked after...
We present a first-principles study of the magnetotransport phenomena in p-doped diamond via exact solution linearized Boltzmann transport equation, which materials' parameters, including electron-phonon and phonon-phonon interactions, are obtained from density functional theory. This approach gives results very good agreement with experimental data for Hall drift mobilities, low- high-field magnetoresistance Seebeck coefficient, phonon-drag effect, range temperatures carrier concentrations....
The issue of tuning the relative height first two dehydrogenation barriers methane (CH4 → CH3 + H and CH2 H) is addressed using density-functional theory. It shown that combination a very active reaction centersuch as Rhwith more inert substratesuch Cu(111)may hinder second step with respect to first, thus resulting in reverse natural order barriers' heights.
We perform a comparative experimental and theoretical study of the temperature dependence up to 700 K frequency linewidths graphite ${E}_{1u}$ ${E}_{2g}$ optical phonons ($\ensuremath{\sim}$1590 1580 cm${}^{\ensuremath{-}1}$) by infrared (IR) Raman spectroscopy. Despite their similar character, two modes is quite different, e.g., shift IR-active mode almost twice as big that Raman-active mode. Ab initio calculations anharmonic properties are in remarkable agreement with measurements explain...
Angle-dispersive x-ray powder diffraction experiments have been performed on yttrium metal up to 183 GPa. We find that the recently discovered $oF16$ structure observed in high-$Z$ trivalent lanthanides is also adopted by above 106 GPa, pressures where it has a superconducting temperature of $\ensuremath{\sim}20$ K. refined both tetragonal and rhombohedral structures against data from preceding ``distorted-fcc'' phase we are unable state categorically which these true this phase. Finally,...
Environmentally sensitive (ES) dyes have been used for many decades to study the lipid order of cell membranes, as different phases play a crucial role in wide variety processes. Yet, understanding how ES behave, interact, and affect membranes at atomistic scale is lacking, partially due lack molecular dynamics (MD) models these dyes. Here, we present ground- excited-state MD commonly dyes, Laurdan di-4-ANEPPDHQ, use simulations behavior disordered an ordered membrane. We also investigate...
The behavior of metals at high pressure is great importance to the fields shock physics, geophysics, astrophysics, and nuclear materials. We study here bulk crystalline aluminum from first principles pressures up $2500\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$---soon within reach laser-based experimental facilities. Our simulations use density-functional theory perturbation in local-density generalized-gradient approximations. Notably, two different exchange-correlation functionals predict...
The dominant phonon wave vectors ${\mathbit{q}}^{*}$ probed by the $2D$ Raman mode of pristine and uniaxially strained graphene are determined via a combination ab initio calculations full two-dimensional integration transition matrix. We show that highly anisotropic rotate about $\mathbit{K}$ with polarizer analyzer condition relative to lattice. corresponding phonon-mediated electronic transitions finite component along $\mathbit{K}$-$\mathbit{\ensuremath{\Gamma}}$ sensitively determines...