Influence of inter-chain correlations on proton ordering in MeHXO4 protonic conductors

Energy spectrum and thermodynamics of the proton subsystem of the crystal w ith chains of hydrogen bonds are investigated, The consideration is based o n the orientational-tunneling model, which includes two types of proton tra nsfer. The strong short-range interactions and the influence of the interna l ordering field arising due to the inter-chain correlations are taken into account. It is shown that under certain conditions the uniform proton dist ribution along the chain becomes unstable. A possible explanation of the pr ecursor effect observed in the CsDSO4 crystal at temperatures below the sup erionic transition point is proposed. (C) 2001 Elsevier Science B.V. All ri ghts reserved.