Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA.
J Phys Condens Matter. 2011 Jan 26;23(3):035501. doi: 10.1088/0953-8984/23/3/035501. Epub 2011 Jan 5.
Ab initio total energy calculations have been performed to study the phase stability of Gd(2)Ti(2)O(7) and Gd(2)Zr(2)O(7) pyrochlores over the pressure range from 0 to 60 GPa. Both compounds are unstable under pressure, and phase transformations to the defect-cotunnite structure are predicted. The phase transformation pressure of 43.6 GPa for Gd(2)Ti(2)O(7) is considerably larger than the value of 13 GPa for Gd(2)Zr(2)O(7), in good agreement with experiments. The decreased structural stability of Gd(2)Zr(2)O(7) under pressure, relative to Gd(2)Ti(2)O(7), is a consequence of the lower compressibility of the ⟨Zr-O⟩ bond and the higher compressibility of the ⟨Gd-O⟩ bond. In addition, the Gd 4f electrons are found to have only a small effect in determining the pressure induced phase transformation.
采用从头算全能量方法研究了 Gd(2)Ti(2)O(7)和 Gd(2)Zr(2)O(7)钙钛矿在 0 到 60 GPa 压力范围内的相稳定性。这两种化合物在压力下都不稳定，预测会发生缺陷钙钛矿结构的相变。Gd(2)Ti(2)O(7)的相变压力为 43.6 GPa，明显大于 Gd(2)Zr(2)O(7)的 13 GPa，与实验结果吻合较好。与 Gd(2)Ti(2)O(7)相比，Gd(2)Zr(2)O(7)在压力下结构稳定性降低，这是由于 ⟨Zr-O⟩键的压缩性较低和 ⟨Gd-O⟩键的压缩性较高所致。此外，发现 Gd 4f 电子对确定压力诱导相变的影响很小。
