SOFTWARE FOCUS Chameleon: A generalized, connectivity altering software for tackling properties of realistic polymer systems Orestis Alexiadis 1 | Nikolaos Cheimarios 1 | Loukas D. Peristeras 2 | Andreas Bick 1 | Vlasis G. Mavrantzas 3 | Doros N. Theodorou 4 | Jörg-Rüdiger Hill 1 | Xenophon Krokidis 1 1 R&D Department, Scienomics SARL, Paris, France 2 Institute of Nanoscience and Nanotechnology, Molecular Thermodynamics and Modelling of Materials Laboratory, National Center for Scientific Research “Demokritos”, Aghia Paraskevi, Greece 3 Department of Chemical Engineering, University of Patras and FORTH/ICE-HT, Patras, Greece 4 School of Chemical Engineering, National Technical University of Athens, Athens, Greece Correspondence Nikolaos Cheimarios, Scienomics SARL, 16 rue de l’Arcade, 75008 Paris, France. Email: nikolaos.cheimarios@scienomics.com Doros N. Theodorou, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, GR-15780 Athens, Greece. Email: doros@central.ntua.gr Present address Vlasis G. Mavrantzas, Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zürich, CH-8092 Zürich, Switzerland. Chameleon, a generalized Monte Carlo software for the phase space analysis of complex, realistic polymer systems is presented. Chameleon implements the so- called connectivity altering technique applied on polymer chains through Monte Carlo moves that do not mimic actual dynamics. These moves enable an accurate and fast sampling of configuration space and produce a robust environment for the prediction of the polymer's properties. Chameleon’s capabilities are presented through a series of computations on well-studied systems, namely polyethylene (PE), polystyrene (PS) and polyvinyl chloride (PVC) in the melt state. PE, PS and PVC are described via a united atom, coarse grained and all atom representation, respectively. The computed structural and volumetric properties of these systems are compared to experimental data and previous computational works, and found to be in excellent agreement. Finally, the shared memory parallel capabilities of Chameleon are presented and quantified in terms of speedup. This article is categorized under: Software > Simulation Methods Structure and Mechanism > Computational Materials Science Theoretical and Physical Chemistry > Statistical Mechanics KEYWORDS atomistic simulations, coarse-grained, connectivity altering, Monte Carlo, parallel 1 | INTRODUCTION Success in product and process design or optimization involves the detailed understanding of materials properties. This can be achieved by systematic experimental analysis of molecular-level characteristics such as the system's architecture, its chemical components, etc. Since this is impractical to do for all possible chemical compositions, the experimental effort needs to be focused on promising candidates. In this direction, molecular modeling and simulations can be of valuable contribution (and sometimes unsurpassed) since they can perform efficiently a smart screening of the few promising candidates for subsequent experimental investigation. This is achieved because by definition molecular simulation directly links the underlying molecular-level characteristics of the materials to their macroscopic properties. Currently, molecular modeling and simulations, such as Molecular Dynamics (MD) and Monte Carlo (MC) are used suc- cessfully in many industrial applications for identifying and characterizing the most promising materials and addressing important questions in various areas of chemical and materials technology, for example, throughput and selectivity of separa- tion processes in porous materials, viscosity of small and medium sized molecules in lubricants and its dependence on addi- tives, mechanical reinforcement in composites, phase equilibria in fluid mixtures and colloidal systems, and many more. Received: 7 November 2018 Revised: 30 January 2019 Accepted: 31 January 2019 DOI: 10.1002/wcms.1414 WIREs Comput Mol Sci. 2019;e1414. wires.wiley.com/compmolsci © 2019 Wiley Periodicals, Inc. 1 of 21 https://doi.org/10.1002/wcms.1414