In the first figure we show the variation of the total energy as a function of the H position along the O-O bond, for different O-O bond lengths of 2.405 Å, 2.469 Å, and 2.510 Å , respectively. Note that the when the O-O bond length is 2.405 Å there is a single minimum at the midpoint. On the other hand, when the O-O bond length increases to 2.469 Å (experimental value) and 2.510 Å, respectively, the energy curve develops a double well, symmetrically placed with respect to the bond center, with the H tunneling between the two equilibrium positions. The effect of the motion of K and P atoms on the ferroelectric transition is shown on the second figure. In these calculations the P and K atoms move out of phase along z. The H atoms are then moved along the O-H-O bonds to determine the equilibrium position. The second Figure shows the variation of total energy as a function of the H position along the O-H-O bond for different values of O-O bond lengths of 2.405 Å, 2.469 Å, and 2.510 Å , respectively. The ab initio calculations reveal that the distance between the two equilibrium positions of H along the O-O bond depend on both the O-O bond length and the displacements of K and P along the z direction, providing new evidence that the ferroelectric transition in H bonded crystals has also a displacive feature.
Please direct questions or comments regarding site content to Linda Gharakhanian. Last updated: December 29, 2003