Atomistic molecular dynamics simulations are used to investigate 1H NMR T1 relaxation of water from paramagnetic Gd3+ ions in solution at 25∘C. Simulations of the T1 relaxivity dispersion function r1 computed from the Gd3+--1H dipole--dipole autocorrelation function agree within ≃8\% of measurements in the range f0≃ 5 ↔ 500 MHz, without any adjustable parameters in the interpretation of the simulations, and without any relaxation models. The simulation results are discussed in the context of the Solomon-Bloembergen-Morgan inner-sphere relaxation model, and the Hwang-Freed outer-sphere relaxation model. Below f0≲ 5 MHz, the simulation overestimates r1 compared to measurements, which is used to estimate the zero-field electron-spin relaxation time. The simulations show potential for predicting r1 at high frequencies in chelated Gd3+ contrast-agents used for clinical MRI.
@article{arxiv.2102.10763,
title = {Molecular dynamics simulations of $^1$H NMR relaxation in Gd$^{3+}$--aqua},
author = {Philip M. Singer and Arjun Valiya Parambathu and Thiago J. Pinheiro dos Santos and Yunke Liu and Lawrence B. Alemany and George J. Hirasaki and Walter G. Chapman and Dilip Asthagiri},
journal= {arXiv preprint arXiv:2102.10763},
year = {2021}
}