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Computer Physics Communications

ISSN: 0010-4655

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Datasets associated with articles published in Computer Physics Communications

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  • gVOF: An open-source package for unsplit geometric volume of fluid methods on arbitrary grids
    The gVOF package implements several accurate and efficient geometric volume of fluid (VOF) methods on arbitrary grids, either structured or unstructured with convex or non-convex cells, based on multidimensional unsplit advection and piecewise linear interface calculation (PLIC) schemes, with the purpose of facilitating and extending the use of advanced unsplit geometric VOF methods in new or existing computational fluid dynamics codes. The package includes a complete and self-contained set of routines for VOF initialization, interface reconstruction and fluid advection, and uses as external libraries a set of publicly available in-house tools to perform several analytical and geometrical operations. These operations may involve handling of high-complex non-convex flux polyhedra, even with self-intersecting faces, which are robustly and efficiently treated in this work without the need of costly techniques based on convex decomposition. Results for the accuracy, computational efficiency, and volume (local and global) conservation properties of different combinations of the implemented advection and reconstruction methods are presented for several numerical tests on structured and unstructured grids. An extensive comparison with results obtained by other authors using advanced geometric VOF methods shows the outstanding performance of the gVOF package in terms of efficiency and accuracy. To demonstrate the performance of the package in solving complex two-phase flow problems, the implemented methods are combined with an existing in-house code to simulate the impact of a water drop on a free surface.
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  • Upcgen: A Monte Carlo simulation program for dilepton pair production in ultra-peripheral collisions of heavy ions
    Ultra-peripheral collisions (UPCs) of heavy ions can be used as a clean environment to study two-photon induced interactions such as dilepton pair photoproduction. Recently, precise data on lepton pair production in UPCs were obtained by the ATLAS experiment at the LHC where significant deviations, of up to 20%, from available theoretical predictions were observed. In this work, we present a Monte Carlo event generator, Upcgen, that implements a refined treatment of the photon flux allowing us to improve the agreement with ATLAS data at large dilepton rapidities. Besides, the new generator offers a possibility to study photon polarization effects and set arbitrary values of the lepton anomalous magnetic moment that can be used in the future studies of tau g - 2 via ditau production measurements in UPCs.
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  • FIESTA5: Numerical high-performance Feynman integral evaluation
    In this paper we present a new release of the FIESTA program (Feynman Integral Evaluation by a Sector decomposiTion Approach). FIESTA5 is performance-oriented — we implemented improvements of various kinds in order to make Feynman integral evaluation faster. We plugged in two new integrators, the Quasi Monte Carlo and Tensor Train. At the same time the old code of FIESTA4 was upgraded to the C++17 standard and mostly rewritten without self-made structures such as hash tables. There are also several essential improvements which are most relevant for complex integrations — the new release is capable of producing results where previously impossible.
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  • DensityTool: A post-processing tool for space- and spin-resolved density of states from VASP
    The knowledge of the local electronic structure of heterogeneous solid materials is crucial for understanding their electronic, magnetic, transport, optical, and other properties. VASP, one of the mostly used packages for density-functional calculations, provides local electronic structure either by projecting the electronic wave functions on atomic spheres, or as a band-decomposed partial charge density. Here, we present a simple tool which takes the partial charge density and the energy eigenvalues calculated by VASP as input and constructs local charge and spin densities. The new data provides a much better spatial understanding than the projection on the atomic spheres. It can be visualized directly in the real space e.g. with Vesta, or averaged along planes spanned by two of the lattice vectors of the periodic unit cell. The plane-averaged local (spin) density of states can be easily plotted e.g. as color-coded data using almost any plotting program. DensityTool can be applied to visualize and understand the local electronic structure of any system calculated with VASP. We expect it to be useful especially for researchers concerned with inhomogeneous systems, such as interfaces, defects, surfaces, adsorbed molecules, or hybrid inorganic-organic composites.
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  • Numerical Regge pole analysis of resonance structures in state-to-state reactive differential cross sections
    This is the third (and the last) code in a collection of three programs [Sokolovski et al. (2011), Akhmatskaya et al. (2014)] dedicated to the analysis of numerical data, obtained in an accurate simulation of an atom-diatom chemical reaction. Our purpose is to provide a detailed description of a FORTRAN code for complex angular momentum (CAM) analysis of the resonance effects in reactive angular scattering [for CAM analysis of integral reactive cross sections see [Akhmatskaya et al. (2014)]. The code evaluates the contributions of a Regge trajectory (or trajectories) to a differential cross section in a specified range of energies. The contribution is computed with the help of the methods described in [Dobbyn et al. (1999), Sokolovski and Msezane (2004), Sokolovski et al. (2007)]. Regge pole positions and residues are obtained by analytically continuing S-matrix element, calculated numerically for the physical integer values of the total angular momentum, into the complex angular momentum plane using the PADE_II program [Sokolovski et al. (2011)]. The code represents a reactive scattering amplitude as a sum of the components corresponding to a rapid “direct” exchange of the atom, and the various scenarios in which the reactants form long-lived intermediate complexes, able to complete several rotations before breaking up into products. The package has been successfully tested on the representative models, as well as the F + H2→ HF+H benchmark reaction. Several detailed examples are given in the text.
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  • Parallel adaptive weakly-compressible SPH for complex moving geometries
    The use of adaptive spatial resolution to simulate flows of practical interest using Smoothed Particle Hydrodynamics (SPH) is of considerable importance. Recently, Muta and Ramachandran [1] have proposed an efficient adaptive SPH method which is capable of handling large changes in particle resolution. This allows the authors to simulate problems with much fewer particles than was possible earlier. The method was not demonstrated or tested with moving bodies or multiple bodies. In addition, the original method employed a large number of background particles to determine the spatial resolution of the fluid particles. In the present work we establish the formulation's effectiveness for simulating flow around stationary and moving geometries. We eliminate the need for the background particles in order to specify the geometry-based or solution-based adaptivity and we discuss the algorithms employed in detail. We consider a variety of benchmark problems, including the flow past two stationary cylinders, flow past different NACA airfoils at a range of Reynolds numbers, a moving square at various Reynolds numbers, and the flow past an oscillating cylinder. We also demonstrate different types of motions using single and multiple bodies. The source code is made available under an open source license, and our results are reproducible.
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  • Tree boosting for learning EFT parameters
    We present a new tree boosting algorithm designed for the measurement of parameters in the context of effective field theory (EFT). To construct the algorithm, we interpret the optimized loss function of a traditional decision tree as the maximal Fisher information in Poisson counting experiments. We promote the interpretation to general EFT predictions and develop a suitable boosting method. The resulting “Boosted Information Tree” algorithm approximates the score, the derivative of the log-likelihood function with respect to the parameter. It thus provides a sufficient statistic in the vicinity of a reference point in parameter space where the estimator is trained. The training exploits per-event information of likelihood ratios for different theory parameter values available in the simulated EFT data sets.
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  • NuSD: A Geant4 based simulation framework for segmented anti-neutrino detectors
    NuSD: Neutrino Segmented Detector is a Geant4-based user application that simulates inverse beta decay events in a variety of segmented scintillation detectors developed by different international collaborations. This simulation framework uses a combination of cross-programs and libraries including Geant4, ROOT and CLHEP developed and used by the high energy physics community. It will enable the neutrino physics community to simulate and study neutrino interactions within different detector concepts using a single program. In addition to neutrino simulations in segmented detectors, this program can also be used for various research projects utilizing scintillation detectors for different physics applications.
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  • Marlics: A finite difference liquid crystal simulation package
    In this paper we present Marlics (Maringá Liquid Crystal Simulator), a software written in C++ to obtain either the system dynamics, by using the Runge-Kutta method, or the minimum energy states with the Fast Inertial Relaxation Engine (FIRE) for both achiral and chiral nematic liquid crystals. The system solved by Marlics consists in the dynamical evolution for the Q-tensor in the Landau-de Gennes formalism for different geometries, including confined slab cells and spherical, liquid crystal droplets. Furthermore, the code accepts custom geometries, so the user may provide a particular geometry of interest to run simulations. The program takes as input a descriptive file giving the simulations parameters and initial conditions, generating a series of different snapshots distributed in time according to the users' needs. Several initial conditions are provided to help the user starting simulations direct to different goals. The code is organized in class modules, which can be modified by the user base to attend their further needs.
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  • LBcuda: A high-performance CUDA port of LBsoft for simulation of colloidal systems
    We present LBcuda, a GPU accelerated version of LBsoft, our open-source MPI-based software for the simulation of multi-component colloidal flows. We describe the design principles, the optimization and the resulting performance as compared to the CPU version, using both an average cost GPU and high-end NVidia GPU cards (V100 and the latest A100). The results show a substantial acceleration for the fluid solver reaching up to 200 GLUPS (Giga Lattice Updates Per Second) on a cluster made of 512 A100 NVIDIA cards simulating a grid of eight billion lattice points. These results open attractive prospects for the computational design of new materials based on colloidal particles.
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