Ewald summation is an important technique for molecular simulation. In this article, expressions are provided for implementing Ewald summation for any inverse power potential in a range of different simulations. Energies, forces, stresses, and Hessian elements as well as truncation errors are considered. Focus is also given to methods for accelerating Ewald summation in Monte Carlo simulations, particularly in the grand canonical ensemble. Ewald techniques are applied to the simulation of CO2 adsorption and diffusion in the metal-organic framework, MOF-5. These simulations show that optimized Ewald summation can provide increased accuracy at similar computational cost compared to that of pair-based methods.

In this article, two new charge equilibration methods for estimating atomic partial charges are outlined. These methods are based on expanding the Taylor series used to estimate the ionization energy of each atom about either the formal or atomic charge, allowing for accurate charge estimation in both covalent and ionic materials. A new treatment of hydrogen atoms based on molecular hydrogen is also introduced. To demonstrate their general applicability, these new methods have been applied to the simulation of CO2 adsorption in metal–organic frameworks. Comparisons with other charge equilibration methods and density functional theory (DFT) calculations show that, of the rapid charge-assigning methods, the algorithm based on atomic ionization best replicates the DFT electrostatic potential and provides the most accurate estimation of CO2 adsorption.

The complexes [Na(CTV)2(OH)(H2O)](H2O)(DMF)2(o-carborane) (3; CTV = cyclotriveratrylene), [K(OH)(CTV)(DMF)]2(o-carborane) (4), [(DMF)(CTV)]2(H2O)4(o-carborane) (5), and (o-carborane)(CTV)(DMF)2 (6) all form as crystalline inclusion complexes from N,N'-dimethylformamide (DMF) solution. Complexes 3 and 4 are the first reported examples of CTV acting as a chelating ligand, with two CTV molecules coordinating cis to the six-coordinate M+ centers (M=Na, K). The extended structures of complexes 3-5 are similar, forming extended coordinate and/or hydrogen-bonding interactions and all feature intracavity complexation of DMF by CTV, while the complex 6 forms an assembly of (o-carborane) intersection of two sets (CTV) ball-and-socket supermolecules with DMF as a channel-type included guest.