Low-energy structures of benzene clusters with a novel accurate potential surface

11 pags.; 9 figs.; 2 tabs.The benzene-benzene (Bz-Bz) interaction is present in severalchemical systems and it is known to be crucial in understand-ing the specificity of important biological phenomena. In thiswork, we propose a novel Bz-Bz analytical potential energysurface which is fine-tuned on accurate ab initio calculations inorder to improve its reliability. Once the Bz-Bz interaction ismodeled, an analytical function for the energy of the Bznclus-ters may be obtained by summing up over all pair potentials.We apply an evolutionary algorithm (EA) to discover thelowest-energy structures of Bznclusters (for n52225), and theresults are compared with previous global optimization studieswhere different potential functions were employed. Besidesthe global minimum, the EA also gives the structures of otherlow-lying isomers ranked by the corresponding energy. Addi-tional ab initio calculations are carried out for the low-lyingisomers of Bz3and Bz4clusters, and the global minimum isconfirmed as the most stable structure for both sizes. Finally, adetailed analysis of the low-energy isomers of the n 5 13 and19 magic-number clusters is performed. The two lowest-energy Bz13isomers show S6and C3symmetry, respectively,which is compatible with the experimental results available inthe literature. The Bz19structures reported here are all non-symmetric, showing two central Bz molecules surrounded by12 nearest-neighbor monomers in the case of the five lowest-energy structures.VC2015 Wiley Periodicals, Inc.Contract grant sponsor: Coimbra Chemistry Centre; Contract grant number: UID/QUI/00313/2013; Contract grant sponsor: Spanish“Ministerio de Ciencia e Innovacion”; Contract grant number: FIS2013-48275-C2-1-P; Contract grant sponsor: Italian Ministry of University and Research (MIUR) for PRIN 2010-2011; Contract grant number: 2010ERFKXL_002. The authors are grateful for the provision of computational time inthe supercomputer resources hosted at Laboratorio de Computación Avançada, Universidade de Coimbra. Allocation of computing timeby CESGA (Spain) is also acknowledged.Peer reviewe

Embedded solutions for a class of highly unstable, underactuated and self-balancing robotic systems

n/

Diagonal Kernel Point Estimation of nth-Order Discrete Volterra-Wiener Systems

The estimation of diagonal elements of a Wiener model kernel is a well-known problem. The new operators and notations proposed here aim at the implementation of efficient and accurate nonparametric algorithms for the identification of diagonal points. The formulas presented here allow a direct implementation of Wiener kernel identification up to the th order. Their efficiency is demonstrated by simulations conducted on discrete Volterra systems up to fifth order

an embedded database technology perspective in cyber physical production systems

Abstract The goal of the paper is the proposition of an enabling technology for the control and optimization of cyber-physical production systems, oriented to the lightweight implementation of performance metrics methodology in a network of distributed devices. The database-centric perspective, applied to distributed devices, supports the adoption of well-known key performance metrics for viable lightweight control policies and optimization of complex scenarios in the factory of the future. An experiment of the technique on a real case data set is presented and analyzed

Graphdiyne based membranes: exceptional performances for helium separation applications

Graphdiyne is a novel two-dimensional material deriving from graphene that has been recently synthesized and featuring uniformly distributed sub-nanometer pores. We report accurate calculations showing that graphdiyne pores permit an almost unimpeded helium transport which can be used for its chemical and isotopic separation. Exceptionally high He/CH_4 selectivities are found which largely exceed the performance of the best membranes used to date for extraction from natural gas. Moreover, by exploiting slight differences in the tunneling probabilities of ^3He and ^4He, we also find promising results for the separation of the Fermionic isotope at low temperature

Enhanced flexibility of the O2 + N2 interaction and Its effect on collisional vibrational energy exchange

12 págs.; 8 figs.; 1 app. This article is part of the Piergiorgio Casavecchia and Antonio Lagana Festschrift special issue.Prompted by a comparison of measured and computed rate coefficients of Vibration-to-Vibration and Vibration-to-Translation energy transfer in O2 + N2 nonreactive collisions, extended semiclassical calculations of the related cross sections were performed to rationalize the role played by attractive and repulsive components of the interaction on two different potential energy surfaces. By exploiting the distributed concurrent scheme of the Grid Empowered Molecular Simulator we extended the computational work to quasiclassical techniques, investigated in this way more in detail the underlying microscopic mechanisms, singled out the interaction components facilitating the energy transfer, improved the formulation of the potential, and performed additional calculations that confirmed the effectiveness of the improvement introduced.The authors acknowledge financial support from the Phys4entry FP7/2007-2013 project (Contract No. 242311), ARPA Umbria, INSTM, the EGI-Inspire project (Contract No. 261323), MIUR PRIN 2008 (2008KJX4SN 003) and 2010/2011 (2010ERFKXL_002), the ESA-ESTEC Contract No. 21790/ 08/NL/HE and the Spanish CTQ2012-37404 and FIS2013- 48275-C2-1-P projects. Computations have been supported by the use of Grid resources and services provided by the European Grid Infrastructure (EGI) and the Italian Grid Infrastructure (IGI) through the COMPCHEM Virtual Organization. Thanks are also due to the COST CMST European Cooperative Project CHEMGRID (Action D37) EGI Inspire.Peer reviewe

Efficiency of Collisional O2 + N2 Vibrational Energy Exchange

10 pags.; 6 figs.; 5 tabs. In press.By following the scheme of the Grid Empowered Molecular Simulator (GEMS), a new O2 + N2 intermolecular potential, built on ab initio calculations and experimental (scattering and second virial coefficient) data, has been coupled with an appropriate intramolecular one. On the resulting potential energy surface detailed rate coefficients for collision induced vibrational energy exchanges have been computed using a semiclassical method. A cross comparison of the computed rate coefficients with the outcomes of previous semiclassical calculations and kinetic experiments has provided a foundation for characterizing the main features of the vibrational energy transfer processes of the title system as well as a critical reading of the trajectory outcomes and kinetic data. On the implemented procedures massive trajectory runs for the proper interval of initial conditions have singled out structures of the vibrational distributions useful to formulate scaling relationships for complex molecular simulations.The authors acknowledge financial support from the Phys4- entry FP7/2007-2013 project (Contract 242311), ARPA Umbria, INSTM, the EGI-Inspire project (Contract 261323), MIUR PRIN 2008 (2008KJX4SN 003) and 2010/2011 (2010ERFKXL_002), the ESA-ESTEC contract 21790/08/ NL/HE, and the Spanish CTQ2012-37404 and FIS2013- 48275-C2-1-P projects. Computations have been supported by the use of Grid resources and services provided by the European Grid Infrastructure (EGI) and the Italian Grid Infrastructure (IGI) through the COMPCHEM Virtual Organization. Thanks are also due to the COST CMST European Cooperative Project CHEMGRID (Action D37) EGI Inspire.Peer reviewe

Transmission of Helium through Graphynes Pores: First Principles Calculations and Quantum Mechanical Simulations

AMOC 2015, Anharmonicity in médium-sized molecules and cluster, CSIC, Madrid (Spain), 26-30 April 2015; http://tct1.iem.csic.es/AMOC2015.htmPeer Reviewe

Full Dimensional Potential Energy Function and Calculation of State-Specific Properties of the CO+N2 Inelastic Processes Within an Open Molecular Science Cloud Perspective

A full dimensional Potential Energy Surface (PES) of the CO + N2 system has been generated by extending an approach already reported in the literature and applied to N2-N2 (Cappelletti et al., 2008), CO2-CO2 (Bartolomei et al., 2012), and CO2-N2 (Lombardi et al., 2016b) systems. The generation procedure leverages at the same time experimental measurements and high-level ab initio electronic structure calculations. The procedure adopts an analytic formulation of the PES accounting for the dependence of the electrostatic and non-electrostatic components of the intermolecular interaction on the deformation of the monomers. In particular, the CO and N2 molecular multipole moments and electronic polarizabilities, the basic physical properties controlling the behavior at intermediate and long-range distances of the interaction components, were made to depend on relevant internal coordinates. The formulated PES exhibits substantial advantages when used for structural and dynamical calculations. This makes it also well suited for reuse in Open Molecular Science Cloud services

Helium nanodroplets as an efficient tool to investigate hydrogen attachment to alkali cations

9 pags., 10 figs. -- This article is part of the themed collection: Stability and properties of new-generation metal and metal-oxide clusters down to subnanometer scaleWe report a novel method to reversibly attach and detach hydrogen molecules to positively charged sodium clusters formed inside a helium nanodroplet host matrix. It is based on the controlled production of multiply charged helium droplets which, after picking up sodium atoms and exposure to H2 vapor, lead to the formation of Nam+(H2)n clusters, whose population was accurately measured using a time-of-flight mass spectrometer. The mass spectra reveal particularly favorable Na+(H2)n and Na2+(H2)n clusters for specific “magic” numbers of attached hydrogen molecules. The energies and structures of these clusters have been investigated by means of quantum-mechanical calculations employing analytical interaction potentials based on ab initio electronic structure calculations. A good agreement is found between the experimental and the theoretical magic numbers.This work was supported by the Austrian Science Fund, FWF (project number P31149) and the Spanish MICINN with Grants FIS2016-79596-P and PID2019-105225GB-I00 (JB, JHR); PID2020- 114654GB-I00/AEI/10.13039/501100011033, 2021-2024 (TGL,MB) and PID2020-114957GB-I00/AEI/10.13039/501100011033 (JCM, MIH). Collaboration has also been supported by the CSIC under i-Link+ program LINKB20041. Allocation of computing time by CESGA (Spain) is also acknowledged.Peer reviewe