Liquid-state paramagnetic relaxation from first principles

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>We simulate nuclear and electron spin relaxation rates in a paramagnetic system from first principles. Sampling a molecular dynamics trajectory with quantum-chemical calculations produces a time series of the instantaneous parameters of the relevant spin Hamiltonian. The Hamiltonians are, in turn, used to numerically solve the Liouville–von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by studying the aqueous solution of the Ni²⁺ ion. Taking advantage of Kubo’s theory, the spin-lattice (<em>T</em>₁) and spin-spin (<em>T</em>₂) relaxation rates are extracted from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available experimental data is obtained by the method.</p></div>