T1relaxation time of water from a molecular dynamics simulation

The T 1 relaxation time of the proton Zeeman magnetization is calculated in a molecular dynamics simulation of two different water models, the single point charge (SPC) model and the polarizable SPC model. First, the possibility to treat such a system as an assembly of independent protons neglecting spin correlations of the two proton spins on the same water molecule is theoretically justified. The relaxation times are then calculated for both water models. This provides a parameter that can directly be compared with the experimental value, and its decomposition in intra- and intermolecular parts gives an indication to where those water models can be improved.