PRESSURE-INDUCED STRUCTURAL-CHANGES IN HGBA2CACU2O6+DELTA

We have developed a set of interatomic potentials for simulation of pr essure-induced structural changes in HgBa2CaCu2O6+delta (Hg-1212) at d elta=0 up to 20 GPa. Our calculated lattice parameter compressibilitie s (a and c), and volume compressibility are 2.50 x 10(-3) GPa(-1), 5.1 7 x 10(-3) GPa(-1) and 10.3 x 10(-3) GPa(-1) respectively, which agree well with experimental values. Our simulations predict that Cu-O2 bon d has a greater compressibility than that of Hg-O2 bond. Moreover, the distance between Ba and O1 along the c-axis, z(Ba-Ol), is nearly unch anged with increasing pressure, whereas the distance between Ba and O2 along the c-axis, z(Ba-O2), decreases dramatically with increasing pr essure. We also predict that the Cu-Ol-Cu bond angle decreases with in creasing pressure. These abnormal structural changes may be related to the pressure-induced charger transfer in Hg-1212.