NMR relaxation and modelling study of the dynamics of SF₆ and Xe in porous organic cages

Abstract

The dynamics of gas in CC3 porous solid is explored with NMR diffusion and relaxation experiments and interpreted with molecular level modeling.

129Xe NMR on Porous Materials: Basic Principles and Recent Applications

“…The same group further studied the relaxation parameters of both xenon and sulfur hexafluoride SF 6 , a potent greenhouse gas, by combining the developed DFT models with experiments. [ 122 ] They elucidated T 1 and T 2 relaxation mechanisms and the different dynamics of the two gases in an organic cage (CC3‐R).…”

Relaxometry models compared with Bayesian techniques: ganglioside micelle example

“…The ideas are implemented in Matlab/octave code 46 and the steps given in flow-chart of parameter estimation (see Core of the MCMC is efficient sampling of configurations (c). For ease of introducing alternative prior distributions the current version, function MCMCstep.m, 46 follow Metropolis algorithm, 7,47,48 hence, the proposed new parameter configurations are sampled at random direction (not for instance guided by likelihood function). Each parameter is given a move individually, following Gibbs sampling algorithm.…”

“…However, provided are a set of tools to monitor convergence and reproducibly and from a moderate computational investment it is clear how challenging (or easy) problem lies ahead. In particular with the option to follow annealing the experience so far is that MCMC can do well in parametrization of NMR-relaxation, relaxometry and line shape studies, 6,7,53,55 and should play an important role in Bayesian evidence calculation.…”

“…3 To obtain more meaningful information from relaxation experiments, relaxation models are utilized to provide details of the mechanisms underlying spin relaxation. 4 Starting from the spinsystem under study relevant mechanism to include may involve dipole-dipole, chemical exchange, paramagnetic and quadrupole contributions, [5][6][7][8][9][10][11][12] as well as chemical shift anisotropy. 13 The challenges in building models involves incorporation of consistent molecular dynamics processes to explain experimental observations and account for spin-dynamics at sufficient accuracy.…”

“…27,28 A deeper understanding of approximations in analytical models as well as a partial or complete reduction of adjustable parameters has been obtained with molecular dynamics simulations. In relaxometry studies this is achieved for paramagnetic relaxation enhancement, 29 rotation and translation of small molecules, 30 water at bilayer interface, 8 water in cement, 31 and ionic liquid, 13 lyotropic phases, 14,32 porous organic cages 7 and proteins. 33 The simulation studies opens for exploration of the validity of analytical models and for some systems serves as the method of choice.…”