The distribution of a molecule's polarizability to individual atomic sites is inevitable to develop accurate polarizable force fields. We present the direct quantum mechanical calculation of atomic polarizabilities of 27 common ionic liquids. The method is superior to previously published distribution routines based on large databases of the molecular polarizability, and enables the correct description of any ionic liquid and its peculiarities within the quantum mechanical framework.

We report an efficient iterative procedure that exploits surface-hopping trajectory methods and quantum dynamics to achieve two complementary purposes: to identify the minimum dimensionality of a molecular Hamiltonian in terms of electronic and nuclear degrees of freedom to study radiationless relaxation mechanisms as well as to provide a reference quantum dynamical calculation that allows assessing of the validity of surface-hopping parameters. This double goal is achieved by a feedback loop between surface hopping and MCTDH calculations based on potential energy surfaces parametrized with a linear vibronic coupling method. Initially, a surface hopping calculation in full dimensionality with a chosen set of parameters is performed, and it is repeated, gradually reducing its dimensionality until divergence with the initial calculation is observed or the system is small enough to be treated quantum dynamically. A comparison between the quantum dynamics and surface hopping simulations dictates the validity of the surface hopping parameters. Using these new parameters, the reduction loop is started again, until convergence. As an example, this strategy is applied to simulate the ultrafast intersystem crossing dynamics of [PtBr 6 ] 2− in solution. The 15-dimensional space initially including 200 electronic states is reduced to a 9-dimensional problem with 76 electronic states, without a considerable loss of accuracy.

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The bioprotective nature of monosaccharides and disaccharides is often attributed to their ability to slow down the dynamics of adjacent water molecules. Indeed, solvation dynamics close to sugars is indisputably retarded compared to bulk water. However, further research is needed on the qualitative and quantitative differences between the water dynamics around different saccharides. Current studies on this topic disagree on whether the disaccharide trehalose retards water to a larger extent than other isomers. Based on molecular dynamics simulation of the time-dependent Stokes shift of a chromophore close to the saccharides trehalose, sucrose, maltose, and glucose, this study reports a slightly stronger retardation of trehalose compared to other sugars at room temperature and below. Calculation and analysis of the intermolecular nuclear Overhauser effect, nuclear quadrupole relaxation, dielectric relaxation spectroscopy, and first shell residence times at room temperature yield further insights into the hydration dynamics of different sugars and confirm that trehalose slows down water dynamics to a slightly larger extent than other sugars. Since the calculated observables span a wide range of timescales relevant to intermolecular nuclear motion, and correspond to different kinds of motions, this study allows for a comprehensive view on sugar hydration dynamics.

We use polarizable molecular dynamics simulations to study the thermal dependence of both structural and dynamic properties of two ionic liquids sharing the same cation (1-ethyl-3-methylimidazolium). The linear temperature trend...