Hydrogen ordering pattern of K3D(SO4)2 in low temperature phase

Abstract

K3D(SO4)2 undergoes a phase transition at Tc = 85 K associated with cell doubling (ax2bx2c) with decreasing temperature. Structure analysis of K3D(SO4)2 was performed by X-ray diffraction experiments at 20 K in order to investigate the structure of the low temperature phase. The excess electrons in the hydrogen-bond were studied by differential fourier synthesis. The excess electrons at room temperature were symmetrically double peaks along the hydrogen-bond while they changed to become asymmetrical along the hydrogen-bond. If we define a dipole moment induced by the deuteron shift patterns in the unit cell, the sum of the dipole moment is almost zero in a larger unit cell, which is consistent with the mode condensation model at the zone boundary point in a reciprocal cell.