<scp>C</scp>hem<scp>S</scp>hell—a modular software package for <scp>QM</scp>/<scp>MM</scp> simulations

<jats:p>ChemShell is a modular computational chemistry package with a particular focus on hybrid quantum mechanical/molecular mechanical (<jats:styled-content style="fixed-case">QM</jats:styled-content>/<jats:styled-content style="fixed-case">MM</jats:styled-content>) simulations. A core set of chemical data handling modules and scripted interfaces to a large number of quantum chemistry and molecular modeling packages underpin a flexible <jats:styled-content style="fixed-case">QM</jats:styled-content>/<jats:styled-content style="fixed-case">MM</jats:styled-content> scheme. ChemShell has been used in the study of small molecules, molecular crystals, biological macromolecules such as enzymes, framework materials including zeolites, ionic solids, and surfaces. We outline the range of <jats:styled-content style="fixed-case">QM</jats:styled-content>/<jats:styled-content style="fixed-case">MM</jats:styled-content> coupling schemes and supporting functions for system setup, geometry optimization, and transition‐state location (including those from the open‐source <jats:styled-content style="fixed-case">DL</jats:styled-content>‐<jats:styled-content style="fixed-case">FIND</jats:styled-content> optimization library). We discuss recently implemented features allowing a more efficient treatment of long range electrostatic interactions, <jats:styled-content style="fixed-case">X</jats:styled-content>‐ray based quantum refinement of crystal structures, free energy methods, and excited‐state calculations. ChemShell has been ported to a range of parallel computers and we describe a number of options including parallel execution based on the message‐passing capabilities of the interfaced packages and task‐farming for applications in which a number of individual <jats:styled-content style="fixed-case">QM</jats:styled-content>, <jats:styled-content style="fixed-case">MM</jats:styled-content>, or <jats:styled-content style="fixed-case">QM</jats:styled-content>/<jats:styled-content style="fixed-case">MM</jats:styled-content> calculations can performed simultaneously. We exemplify each of the features by brief reference to published applications.</jats:p><jats:p>This article is categorized under: <jats:list list-type="explicit-label"> <jats:list-item><jats:p>Software > Quantum Chemistry</jats:p></jats:list-item> <jats:list-item><jats:p>Software > Molecular Modeling</jats:p></jats:list-item> </jats:list></jats:p>