Encapsulation of a Water Molecule inside C Fullerene: The Impact of Confinement on Quantum Features.

We introduce an efficient quantum fully coupled computational scheme within the multiconfiguration time-dependent Hartree (MCTDH) approach to handle the otherwise extremely costly computations of translational-rotational-vibrational states and energies of light-molecule endofullenes. Quantum calculations on energy levels are reported for a water molecule inside C fullerene by means of such a systematic approach that includes all nine degrees of freedom of HO@C and does not consider restrictions above them. The potential energy operator is represented as a sum of natural potentials employing the -mode expansion, along with the exact kinetic energy operator, by introducing a set of Radau internal coordinates for the HO molecule.

Statistical mechanics study of the introduction of a vaccine against COVID-19 disease.

By the end of 2020, a year since the first cases of infection by the Covid-19 virus have been reported; several pharmaceutical companies made significant progress in developing effective vaccines against the Covid-19 virus that has claimed the lives of more than 10^{6} people over the world. On the other hand, there is growing evidence of re-infection by the virus, which can cause further outbreaks. In this paper, we apply statistical physics tools to examine theoretically the vaccination rate required to control the pandemic for three different vaccine efficiency scenarios and five different vaccination rates.

Variational Monte Carlo Calculations of A≤4 Nuclei with an Artificial Neural-Network Correlator Ansatz.

The complexity of many-body quantum wave functions is a central aspect of several fields of physics and chemistry where nonperturbative interactions are prominent. Artificial neural networks (ANNs) have proven to be a flexible tool to approximate quantum many-body states in condensed matter and chemistry problems. In this work we introduce a neural-network quantum state ansatz to model the ground-state wave function of light nuclei, and approximately solve the nuclear many-body Schrödinger equation.

Multifunctionality of Reduced Graphene Oxide in Bioderived Polylactide/Poly(Dodecylene Furanoate) Nanocomposite Films.

This work reports on the first attempt to prepare bioderived polymer films by blending polylactic acid (PLA) and poly(dodecylene furanoate) (PDoF). This blend, containing 10 wt% PDoF, was filled with reduced graphene oxide (rGO) in variable weight fractions (from 0.25 to 2 phr), and the resulting nanocomposites were characterized to assess their microstructural, thermal, mechanical, optical, electrical, and gas barrier properties.

Computational Characterization of Astrophysical Species: The Case of Noble Gas Hydride Cations.

Theoretical-computational studies together with recent astronomical observations have shown that under extreme conditions in the interstellar medium (ISM), complexes of noble gases may be formed. Such observations have generated a wide range of possibilities. In order to identify new species containing such atoms, the present study gathers spectroscopic data for noble gas hydride cations, NgH (Ng = He, Ne, Ar) from high-level quantum chemistry computations, aiming to contribute in understanding the chemical bonding and electron sharing in these systems.

Computational density-functional approaches on finite-size and guest-lattice effects in CO@sII clathrate hydrate.

We performed first-principles computations to investigate guest-host/host-host effects on the encapsulation of the CO molecule in sII clathrate hydrates from finite-size clusters up to periodic 3D crystal lattice systems. Structural and energetic properties were first computed for the individual and first-neighbors clathrate-like sII cages, where highly accurate ab initio quantum chemical methods are available nowadays, allowing in this way the assessment of the density functional (DFT) theoretical approaches employed. The performance of exchange-correlation functionals together with recently developed dispersion-corrected schemes was evaluated in describing interactions in both short-range and long-range regions of the potential.

Exploring CO @sI Clathrate Hydrates as CO Storage Agents by Computational Density Functional Approaches.

The formation of specific clathrate hydrates and their transformation at given thermodynamic conditions depends on the interactions between the guest molecule/s and the host water lattice. Understanding their structural stability is essential to control structure-property relations involved in different technological applications. Thus, the energetic aspects relative to CO @sI clathrate hydrate are investigated through the computation of the underlying interactions, dominated by hydrogen bonds and van der Waals forces, from first-principles electronic structure approaches.

Modelling interactions of cationic dimers in He droplets: microsolvation trends in HeK clusters.

We report the results of a detailed theoretical investigation of small K-doped He clusters. The structural characteristics and stabilities of such cations are determined from ab initio electronic structure calculations at the MRCI+Q level of theory. The underlying interactions show a multireference character and such effects are analyzed.

Taking snapshots of a quantum thermalization process: Emergent classicality in quantum jump trajectories.

We investigate theoretically the emergence of classical statistical physics in a finite quantum system that is either totally isolated or otherwise subjected to a quantum measurement process. We show via a random matrix theory approach to nonintegrable quantum systems that the set of outcomes of the measurement of a macroscopic observable evolve in time like stochastic variables, whose variance satisfies the celebrated Einstein relation for Brownian diffusion. Our results show how to extend the framework of eigenstate thermalization to the prediction of properties of quantum measurements on an otherwise closed quantum system.

Structural Stability of the CO @sI Hydrate: a Bottom-Up Quantum Chemistry Approach on the Guest-Cage and Inter-Cage Interactions.

Through reliable first-principles computations, we have demonstrated the impact of CO molecules enclathration on the stability of sI clathrate hydrates. Given the delicate balance between the interaction energy components (van der Waals, hydrogen bonds) present on such systems, we follow a systematic bottom-up approach starting from the individual 5 and 5 6 sI cages, up to all existing combinations of two-adjacent sI crystal cages to evaluate how such clathrate-like models perform on the evaluation of the guest-host and first-neighbors inter-cage effects, respectively. Interaction and binding energies of the CO occupation of the sI cages were computed using DF-MP2 and different DFT/DFT-D electronic structure methodologies.

Thermally Induced Diffusion and Restructuring of Iron Triade (Fe, Co, Ni) Nanoparticles Passivated by Several Layers of Gold.

The temperature-induced structural changes of Fe-, Co-, and Ni-Au core-shell nanoparticles with diameters around 5 nm are studied via atomically resolved transmission electron microscopy. We observe structural transitions from local toward global energy minima induced by elevated temperatures. The experimental observations are accompanied by a computational modeling of all core-shell particles with either centralized or decentralized core positions.

Microdosimetric measurements as a tool to assess potential in-field and out-of-field toxicity regions in proton therapy.

Relative biological effectiveness (RBE) variations are thought to be one of the primary causes of unexpected normal-tissue toxicities during tumor treatments with charged particles. Unlike carbon therapy, where treatment planning is optimized on the basis of the RBE-weighted dose, a constant RBE value of 1.1 is currently used in proton therapy.

He Inclusion in Ice-like and Clathrate-like Frameworks: A Benchmark Quantum Chemistry Study of Guest-Host Interactions.

Energetics and structural properties of selected type and size He@hydrate frameworks, e.g., from regular structured ice channels to clathrate-like cages, are presented from first-principles quantum chemistry methods.

Hybrid optical fiber for light-induced superconductivity.

We exploit the recent proposals for the light-induced superconductivity mediated by a Bose-Einstein condensate of exciton-polaritons to design a superconducting fiber that would enable long-distance transport of a supercurrent at elevated temperatures. The proposed fiber consists of a conventional core made of a silica glass with the first cladding layer formed by a material sustaining dipole-polarised excitons with a binding energy exceeding 25 meV. To be specific, we consider a perovskite cladding layer of 20 nm width.

Finite Systems under Pressure: Assessing Volume Definition Models from Parallel-Tempering Monte Carlo Simulations.

We have investigated different approaches to handling parallel-tempering Monte Carlo (PTMC) simulations in the isothermal-isobaric ensemble of molecular cluster/nanoparticle systems for predicting structural phase diagram transitions. We have implemented various methodologies that consist of treating pressure implicitly through its effect on the volume. Thus, the main problem in the simulations under nonzero pressure becomes the volume definition of the finite nonperiodic system, and we considered approaches based on the particles' coordinates.

Smart Buildings IoT Networks Accuracy Evolution Prediction to Improve Their Reliability Using a Lotka-Volterra Ecosystem Model.

Internet of Things (IoT) is the paradigm that has largely contributed to the development of smart buildings in our society. This technology makes it possible to monitor all aspects of the smart building and to improve its operation. One of the main challenges encountered by IoT networks is that the the data they collect may be unreliable since IoT devices can lose accuracy for several reasons (sensor wear, sensor aging, poorly constructed buildings, etc.

Theoretical Study of Cationic Alkali Dimers Interacting with He: Li-He and Na-He van der Waals Complexes.

We present a theoretical study on the potential energy surface and bound states of He-A complexes, where A is one of the alkali Li or Na atoms. The intermolecular interactions were systematically investigated by high-level electronic structure computations, and the corresponding raw data were then employed to reproduce accurate analytical expressions of the potential surfaces. In turn, we used these potentials to evaluate bound configurations of the trimers from nuclear quantum calculations and to extract information on the effect of orientational anisotropy of the forces and the interplay between repulsive and attractive interaction within the potential surfaces.

Optical properties and pulse shape discrimination in siloxane-based scintillation detectors.

The possibility to detect fast neutrons as a distinct signal from that one of γ-rays background is surely of great importance for several topics, spanning from homeland security to radiation monitoring in nuclear physics research plants. Nowadays, Helium-3 based detectors are extremely expensive, while the use of large volume liquid scintillators presents serious concerns related to spillage risks and waste disposal. A very attractive alternative is the use of commercially available solid scintillators, which exploits an aromatic polymer matrix entrapping very high loadings of primary dye, thereby enabling the use of pulse shape analysis (PSA) to discriminate between fast neutrons and γ-rays.

Quantum chaotic fluctuation-dissipation theorem: Effective Brownian motion in closed quantum systems.

We analytically describe the decay to equilibrium of generic observables of a nonintegrable system after a perturbation in the form of a random matrix. We further obtain an analytic form for the time-averaged fluctuations of an observable in terms of the rate of decay to equilibrium. Our result shows the emergence of a fluctuation-dissipation theorem corresponding to a classical Brownian process, specifically, the Ornstein-Uhlenbeck process.

Nuclear Charge Radii of ^{10,11}B.

The first laser spectroscopic determination of the change in the nuclear charge radius for a five-electron system is reported. This is achieved by combining high-accuracy ab initio mass-shift calculations and a high-accuracy measurement of the isotope shift in the 2s^{2}2p  ^{2}P_{1/2}→2s^{2}3s  ^{2}S_{1/2} ground state transition in boron atoms. Accuracy is increased by orders of magnitude for the stable isotopes ^{10,11}B and the results are used to extract their difference in the mean-square charge radius ⟨r_{c}^{2}⟩^{11}-⟨r_{c}^{2}⟩^{10}=-0.

Fully Coupled Quantum Treatment of Nanoconfined Systems: A Water Molecule inside a Fullerene C.

We implemented a systematic procedure for treating the quantal rotations by including all translational and vibrational degrees of freedom for any triatomic bent molecule in any embedded or confined environment, within the MCTDH framework. Fully coupled quantum treatments were employed to investigate unconventional properties in nanoconfined molecular systems. In this way, we facilitate a complete theoretical analysis of the underlying dynamics that enables us to compute the energy levels and the nuclear spin isomers of a single water molecule trapped in a C fullerene cage.

A Systematic Protocol for Benchmarking Guest-Host Interactions by First-Principles Computations: Capturing CO in Clathrate Hydrates.

Clathrate hydrates of CO have been proposed as potential molecular materials in tackling important environmental problems related to greenhouse gases capture and storage. Despite the increasing interest in such hydrates and their technological applications, a molecular-level understanding of their formation and properties is still far from complete. Modeling interactions is a challenging and computationally demanding task, essential to reliably determine molecular properties.

Validity of Weyl fermion picture for transition metals monopnictides TaAs, TaP, NbAs, and NbP from ab initio studies.

We investigate electronic and optical properties of the topological Weyl semimetals TaAs, TaP, NbAs and NbP crystallizing in bct geometry by means of the ab initio density functional theory with spin-orbit interaction within the independent-particle approximation. The small energetical overlap of Ta5d or Nb4d derived conduction and valence bands leads to electron and/or hole pockets near the Fermi energy at the 24 Weyl nodes. The nodes give rise to two-(three-)dimensional Dirac cones for the W (W) Weyl type.

Assessing Intermolecular Interactions in Guest-Free Clathrate Hydrate Systems.

Recently, empty hydrate structures sI, sII, sH, and others have been proposed as low-density ice structures by both experimental observations and computer simulations. Some of them have been synthesized in the laboratory, which motivates further investigations on the stability of such guest-free clathrate structures. Using semiempirical and ab initio-based water models, as well as dispersion-corrected density functional theory approaches, we predict their stability, including cooperative many-body effects, in comparison with reference data from converged wave function-based DF-MP2 electronic structure calculations.