Relaxation dynamics of disordered Ising model. Two-site cluster   approximation
  Spin relaxation in a site-disordered Ising model within master equation approach is studied. The $\vec{q},\omega$-dependent susceptibility of the model is calculated and investigated. Effects described by the two-site cluster approximation and lost by the mean field approximation are discussed. Comparison of obtained results with dielectric measurements in $Cs(H_{1-x}D_x)_2PO_4$ is presented. 
R.R.Levitskii, S.I.Sorokov, R.O.Sokolovskii