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We present a toolkit that allows for the preparation of QM/MM input files from a conformational ensemble of molecular geometries. The package is currently compatible with trajectory and topology files in Amber, CHARMM, GROMACS and NAMD formats, and has the possibility to generate QM/MM input files for Gaussian (09 and 16), Orca (≥4.0), NWChem and (Open)Molcas. The toolkit can be used in command line, so that no programming experience is required, although it presents some features that can also be employed as a python application programming interface. We apply the toolkit in four situations in which different electronic‐structure properties of organic molecules in the presence of a solvent or a complex biological environment are computed: the reduction potential of the nucleobases in acetonitrile, an energy decomposition analysis of tyrosine interacting with water, the absorption spectrum of an azobenzene derivative integrated into a voltage‐gated ion channel, and the absorption and emission spectra of the luciferine/luciferase complex. These examples show that the toolkit can be employed in a manifold of situations for both the electronic ground state and electronically excited states. It also allows for the automatic correction of the active space in the case of CASSCF calculations on an ensemble of geometries, as it is shown for the azobenzene derivative photoswitch case. [ABSTRACT FROM AUTHOR]

The characterization of the nature of bonds in a series of gas-phase all-metal clusters containing the [Al.sub.4] unit attached to an alkaline, alkaline earth, or transition metal is presented. The results suggest that the [Al.sub.4.sup.2-] system is stabilized by the cations [M.sup.}/[M.sup.2} when M is a light alkaline and alkaline earth metal and destabilized by the transition metal cations.

Two different atomic partitioning were used to study atomic charges and delocalization indexes (DIs) for a series of carbonyl compounds. These compounds are comprised of dimethyl ketone, acetaldehyde, acetic acid, methyl acetate, acetamide, methyl vinyl ketone, divinyl ketone, and benzoic acid.