Local-field approximation of homonuclear dipolar interactions in 7Li-NMR: Density-matrix calculations and random-walk simulations tested by echo experiments on borate glasses

Illustration of the local dipolar field model. Due to the translational motion of adjacent spins βi on the coordination shell a trajectory of the NMR frequency ωD(α) at the centered spin site α is generated. The resulting distribution function G(ωD(α)) is shown.