Proton Spin-Lattice Relaxation in Organic Molecular Solids: Polymorphism and the Dependence on Sample Preparation

We report solid‐state nuclear magnetic resonance 1H spin‐lattice relaxation, single‐crystal X‐ray diffraction, powder X‐ray diffraction, field emission scanning electron microscopy, and differential scanning calorimetry in solid samples of 2‐ethylanthracene (EA) and 2‐ethylanthraquinone (EAQ) that have been physically purified in different ways from the same commercial starting compounds. The solid‐state 1H spin‐lattice relaxation is always non‐exponential at high temperatures as expected when CH3 rotation is responsible for the relaxation. The 1H spin‐lattice relaxation experiments are very sensitive to the “several‐molecule” (clusters) structure of these van der Waals molecular solids. In the three differently prepared samples of EAQ, the relaxation also becomes very non‐exponential at low temperatures. This is very unusual and the decay of the nuclear magnetization can be fitted with both a stretched exponential and a double exponential. This unusual result correlates with the powder X‐ray diffractometry results and suggests that the anomalous relaxation is due to crystallites of two (or more) different polymorphs (concomitant polymorphism)

PetaFLOP Molecular Dynamics for Engineering Applications

Molecular dynamics (MD) simulations enable the investigation of multicomponent and multiphase processes relevant to engineering applications, such as droplet coalescence or bubble formation. These scenarios require the simulation of ensembles containing a large number of molecules. We present recent advances within the MD framework ls1 mardyn which is being developed with particular regard to this class of problems. We discuss several OpenMP schemes that deliver optimal performance at node-level. We have further introduced nonblocking communication and communication hiding for global collective operations. Together with revised data structures and vectorization, these improvements unleash PetaFLOP performance and enable multi-trillion atom simulations on the HLRS supercomputer Hazel Hen. We further present preliminary results achieved for droplet coalescence scenarios at a smaller scale.BMBF, 01IH16008, Verbundprojekt: TaLPas - Task-basierte Lastverteilung und Auto-Tuning in der Partikelsimulatio

NMR Study of Ion Motions in [C(NH2\text{}_{2})3\text{}_{3}]3\text{}_{3}GaF6\text{}_{6}

Proton and fluorine spin-lattice relaxation times as well as second moments were measured in guanidinium hexafluorogallate over a wide range of temperature. The analysis of all cross-relaxation effects occurring in the four unlike spin system revealed two cation motions and yielded their activation parameters. It was found that the anion size did not influence C$\text{}_{3}$ reorientation of cation nor isotropic reorientation of anion

ACTA PHYSICA POLONICA A NMR STUDY OF ION MOTIONS IN [C(NH 2 ) 3 ] 3 GaF6

Proton and fluorine spin-lattice relaxation times as well as second moments were measured in guanidinium hexafluorogallate over a wide range of temperature. The analysis of all cross-relaxation effects occurring in the four unlike spin system revealed two cation motions and yielded their activation parameters. It was found that the anion size did not influence C3 reorientation of cation nor isotropic reorientation of anion