Deuteron Tunneling and Phase Transition in M_3D(A0_4)_2 Antiferroelectrics

摘要

An effect of the AO_4 tetrahedron reorganization vibrational modes on the deuteron tunneling splitting DELTA_D is treated for fully deuterated M_3D(AO_4)_2 materials (M alkali metal;A = S,Se) of the TKHS family using various quantum chemical models and computational techniques.It is found that the reorganization of the nonhydrogen framework of the D(AO_4)~(3-)_2 dimers in a crystal results in the reduction of DELTA_D and favors the transition of a material in the ordered (antiferroelectric) phase.Numerical estimation of this effect with the use of the available diffraction data leDELTA_Ds to only minor reduction of DELTA_D.At the same time,substantial pronounced contributions to DELTA_D reduction is due to the corrections of potential energy profiles,calculated by different quantum chemical techniques.