Efficient full frequency GW for metals using a multipole approach for the dielectric screening

The properties of metallic systems with important and structured excitations at low energies, such as Cu, are challenging to describe with simple models like the plasmon pole approximation (PPA), and more accurate and sometimes prohibitive full frequency approaches are usually required.

Quenching of low-energy optical absorption in bilayer C3N polytypes

In this work we provide a first-principles description of the electronic and optical properties of bilayers C3N, with different stacking motifs AB, AB', and AA'. Starting from quasiparticle electronic band structures, we solve the Bethe-Salpeter equation (BSE) to access the excitonic properties of these bilayers. For all stacking sequences, we see strong optical absorption at energies lower than but close to that of the monolayer. Most relevant, we predict a strong quenching of the low-energy optical absorption, with negligible oscillator strengths of low-lying bound excitons.

Dielectric response and excitations of hydrogenated free-standing graphene

The conversion of semimetallic suspended graphene (Gr) to a large-gap semiconducting phase is here realized by controlled adsorption of atomic hydrogen (deuterium) on free-standing nanoporous Gr veils. This approach allows to achieve a very clean and neat adsorption, overcoming any spurious influence associated to the presence of substrates. The effects of local rehybridization from sp2 to sp3 chemical bonding are investigated by combining X-ray photoelectron spectroscopy and high-resolution electron energy-loss spectroscopy (HREELS) with ab-initio based modelling.

Towards high-throughput many-body perturbation theory: efficient algorithms and automated workflows

The automation of ab initio simulations is essential in view of performing high-throughput (HT) computational screenings oriented to the discovery of novel materials with desired physical properties. In this work, we propose algorithms and implementations that are relevant to extend this approach beyond density functional theory (DFT), in order to automate many-body perturbation theory (MBPT) calculations.

Efficient GW calculations in two dimensional materials through a stochastic integration of the screened potential

Many-body perturbation theory methods, such as the G0W0 approximation, are able to accurately predict quasiparticle (QP) properties of several classes of materials. However, the calculation of the QP band structure of two-dimensional (2D) semiconductors is known to require a very dense BZ sampling, due to the sharp q-dependence of the dielectric matrix in the long-wavelength limit (q → 0).

HP – A code for the calculation of Hubbard parameters using density-functional perturbation theory

The authors introduce HP, an implementation of density-functional perturbation theory, designed to compute Hubbard parameters (on-site U and inter-site V) in the framework of DFT+U and DFT+U+V. The code does not require the use of computationally expensive supercells of the traditional linear-response approach; instead, unit cells are used with monochromatic perturbations that significantly reduce the computational cost of determining Hubbard parameters. HP is an open-source software distributed under the terms of the GPL as a component of Quantum ESPRESSO.

turboMagnon – A code for the simulation of spin-wave spectra using the Liouville-Lanczos approach to time-dependent density-functional perturbation theory

The authors introduce turboMagnon, an implementation of the Liouville-Lanczos approach to linearized time-dependent density-functional theory, designed to simulate spin-wave spectra in solid-state materials. The code is based on the noncollinear spin-polarized framework and the self-consistent inclusion of spin-orbit coupling that allow to model complex magnetic excitations. The spin susceptibility matrix is computed using the Lanczos recursion algorithm that is implemented in two flavors - the non-Hermitian and the pseudo-Hermitian one.

Optimal model of semi-infinite graphene for ab initio calculations of reactions at graphene edges by the example of zigzag edge reconstruction

The authors investigate how parameters of the model of semi-infinite graphene based on a graphene nanoribbon under periodic boundary conditions affect the accuracy of ab initio calculations of reactions at graphene edges by the example of the first stage of reconstruction of zigzag graphene edges, formation of a pentagon-heptagon pair. It is shown that to converge properly the results, the nanoribbon should consist of at least 6 zigzag rows and periodic images of the pair along the nanoribbon axis should be separated by at least 6 hexagons.

Engineering of metal-MoS2 contacts to overcome Fermi level pinning

Fermi level pinning (FLP) in metal-MoS2 contacts induces large Schottky barrier heights which in turn results in large contact resistances. In this work, we made use of Density Functional Theory (DFT) to study the origin of FLP in MoS2 contacts with a variety of metals. We also reported how the Fermi level de-pinning could be attained by controlling the distance between the metal and MoS2. In this respect, the metal-MoS2 contacts can be engineered by means of the insertion of proper buffer layers and the use of back-gated structures.

Viscosity in water from first-principles and deep-neural-network simulations

In this paper, the authors report on an extensive study of the viscosity of liquid water at near-ambient conditions, performed within the Green-Kubo theory of linear response and equilibrium ab initio molecular dynamics (AIMD), based on density-functional theory (DFT).

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