Gap Opening in Double-Sided Highly Hydrogenated Free-Standing Graphene

Conversion of free-standing graphene into pure graphane─where each C atom is sp3 bound to a hydrogen atom─has not been achieved so far, in spite of numerous experimental attempts. Here, we obtain an unprecedented level of hydrogenation (≈90% of sp3 bonds) by exposing fully free-standing nanoporous samples─constituted by a single to a few veils of smoothly rippled graphene─to atomic hydrogen in ultrahigh vacuum.

Competition between Ta-Ta and Te-Te bonding leading to the commensurate charge density wave in TaTe4

The origin of the charge density wave in TaTe4 is discussed on the basis of a first-principles density functional theory analysis of the Fermi surface, electron-hole response function, phonon band structure of the average structure, and structural optimization of the modulated phase. Analysis of the band structure and Fermi surface of the average structure clearly proves that despite the presence of TaTe4 chains in the crystal structure, TaTe4 is in fact a 3D material as far as the electronic structure near the Fermi level is concerned.

Surface termination dependence of electronic and optical properties in Ti2CO2 MXene monolayers

Two-dimensional (2D) MXenes are a rapid growing family of 2D materials with rich physical and chemical properties where their surface termination plays an essential role. Among the various 2D MXenes, functionalization of the TinCn−1 phase with oxygen (O) atoms makes them attractive for optoelectronic applications due to their optical gap residing in the infrared or visible region. In this paper, the authors theoretically investigate the electronic and optical properties of four different O-atom-functionalized TinCn−1 MXene monolayers using state-of-the-art, first-principles techniques.

Temperature- and vacancy-concentration-dependence of heat transport in Li3ClO from multi-method numerical simulations

Despite governing heat management in any realistic device, the microscopic mechanisms of heat transport in all-solid-state electrolytes are poorly known: existing calculations, all based on simplistic semi-empirical models, are unreliable for superionic conductors and largely overestimate their thermal conductivity. In this work, we deploy a combination of state-of-the-art methods to calculate the thermal conductivity of a prototypical Li-ion conductor, the Li3ClO antiperovskite.

Full orbital decomposition of Yu-Shiba-Rusinov states based on first principles

The authors have implemented the Bogoliubov–de Gennes equation in a screened Korringa-Kohn-Rostoker method for solving, self-consistently, the superconducting state for three-dimensional (3D) crystals including substitutional impurities. In this paper the authors extend this theoretical framework to allow for collinear magnetism and apply it to fcc Pb with 3D magnetic impurities. In the presence of magnetic impurities, there is a pair-breaking effect that results in in-gap Yu-Shiba-Rusinov (YSR) states which we decompose into contributions from the individual orbital character.

Magnetic properties of coordination clusters with {Mn4} and {Co4} antiferromagnetic cores

The authors present a joint experimental and theoretical characterization of the magnetic properties of coordination clusters with an antiferromagnetic core of four magnetic ions. Two different compounds are analyzed, with Co and Mn ions in the core. While both molecules are antiferromagnetic, they display different sensitivities to external magnetic field, according to the different atomic magnetic moments and strength of the intra-molecular magnetic couplings.

Merging of superfluid helium nanodroplets with vortices

Within density functional theory, the authors have investigated the coalescence dynamics of two superfluid helium nanodroplets hosting vortex lines in different relative orientations, which are drawn towards each other by the Van der Waals mutual attraction. The authors have found a rich phenomenology depending on how the vortex lines are oriented. In particular, when a vortex and antivortex lines are present in the merging droplets, a dark soliton develops at the droplet contact region, which eventually decays into vortex rings.

Heat transport in liquid water from first-principles and deep-neural-network simulations

The authors compute the thermal conductivity of water within linear response theory from equilibrium molecular dynamics simulations, by adopting two different approaches. In one, the potential energy surface (PES) is derived on the fly from the electronic ground state of density functional theory (DFT) and the corresponding analytical expression is used for the energy flux. In the other, the PES is represented by a deep neural network (DNN) trained on DFT data, whereby the PES has an explicit local decomposition and the energy flux takes a particularly simple expression.

Solution to the Modified Helmholtz Equation for Arbitrary Periodic Charge Densities

The authors present a general method for solving the modified Helmholtz equation without shape approximation for an arbitrary periodic charge distribution, whose solution is known as the Yukawa potential or the screened Coulomb potential. The method is an extension of Weinert’s pseudo-charge method [Weinert M, J Math Phys, 1981, 22:2433–2439] for solving the Poisson equation for the same class of charge density distributions. The inherent differences between the Poisson and the modified Helmholtz equation are in their respective radial solutions.

Thermal and Tidal Evolution of Uranus with a Growing Frozen Core

The origin of the very low luminosity of Uranus is unknown, as is the source of the internal tidal dissipation required by the orbits of the Uranian moons. Models of the interior of Uranus often assume that it is inviscid throughout, but recent experiments show that this assumption may not be justified; most of the interior of Uranus lies below the freezing temperature of H2O. The authors find that the stable solid phase of H2O, which is superionic, has a large viscosity controlled by the crystalline oxygen sublattice.

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