Perspective: Explicitly correlated electronic structure theory for complex systems Perspective: Computing (ro-)vibrational spectra of molecules with more than four atoms A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H Today's quantum chemistry methods are extremely powerful but rely upon complex quantities such as the massively multidimensional wavefunction or even the simpler electron density. Consequently, chemical insight and a chemist's intuition are often lost in this complexity leaving the results obtained difficult to rationalize. To handle this overabundance of information, computational chemists have developed tools and methodologies that assist in composing a more intuitive picture that permits better understanding of the intricacies of chemical behavior. In particular, the fundamental comprehension of phenomena governed by non-covalent interactions is not easily achieved in terms of either the total wavefunction or the total electron density, but can be accomplished using more informative quantities. This perspective provides an overview of these tools and methods that have been specifically developed or used to analyze, identify, quantify, and visualize non-covalent interactions. These include the quantitative energy decomposition analysis schemes and the more qualitative class of approaches such as the Non-covalent Interaction index, the Density Overlap Region Indicator, or quantum theory of atoms in molecules. Aside from the enhanced knowledge gained from these schemes, their strengths, limitations, as well as a roadmap for expanding their capabilities are emphasized. ©2017Author(s).All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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Microporous organic molecular crystals (MOMCs) are materials composed of discrete organic molecules interacting noncovalently. The gas uptake of CO 2 , CH 4 , N 2 , and Xe in one of the most widely investigated MOMCs, trispiro(benzodioxole[2′.2:2″.4:2‴.6]1,3,5,2,4,6-triazatriphosphinine) (1), was computed by grand canonical Monte Carlo (GCMC) simulations based on our lately developed force field method vdW3, which is fitted to accurate ab initio potentials (double hybrid functional B2PLYP with a D3 dispersion correction using def2-TZVPP basis sets). The B2PLYP-D3 results compare very well with CCSD(T)/CBS interaction energies for benzene−gas model complexes. Our multiscale modeling approach to accurate interaction potentials is found to be essential in order to obtain reasonable adsorption isotherms and heats of adsorption. The good agreement between the simulation results and experimental data in all cases gives us the opportunity to design novel complex materials for gas adsorption based solely on first-principles calculations.