论文部分内容阅读
Based on the results of total-energy calculations for embedded clusters using self-consistent-field Xα-scatteredwave method, we determined the tetragonal fine structure of K(Ta0.56Nb0.44 ) Os, i.e., the equilibrium configuration of B-site cations (Ta and Nb) in the ferroelectric phase. Ta is found to have an off-center displacement of about 0.02A along [001]. The off-center displacement of Nb is much larger than that of Ta, thus it makes a major contribution to the occurrence of the ferroelectric instability.