摘要
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(Ta_(0.56)Nb_(0.44))O_(3),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.
基金
Supported by the Doctoral Fund of the State Education Commission of China under Grant No.98042211.
