Macroscopic nuclear spin diffusion constants of rotating polycrystalline solids from first-principles simulation
A method for quantitatively calculating nuclear spin diffusion constants directly from crystal structures is introduced. This approach uses the first-principles low-order correlations in Liouville space (LCL) method to simulate spin diffusion in a box, starting from atomic geometry and including both magic-angle spinning (MAS) and powder averaging. The LCL simulations are fit to the 3D diffusion equation to extract quantitative nuclear spin diffusion constants. We demonstrate this method for the case of H-1 spin diffusion in ice and L-histidine, obtaining diffusion constants that are consistent with literature values for H-1 spin diffusion in polymers and that follow the expected trends with respect to magic-angle spinning rate and the density of nuclear spins. In addition, we show that this method can be used to model C-13 spin diffusion in diamond and therefore has the potential to provide insight into applications such as the transport of polarization in non-protonated systems. (C) 2015 Elsevier Inc. All rights reserved.