中文摘要：

本文采用密度泛函理论中的广义梯度近似和赝势平面波方法对BiTiO3和BiVO3的稳定性进行了第一性原理计算和相图研究，预测他们在热力学平衡条件下的稳定性。结果表明，这两种物质都很难在热力学平衡条件下稳定。因此，合成这两种物质时，应该考虑热力学平衡之外的其他方法。

英文摘要：

The stabilities of BiTiO3 and BiVO3 under thermodynamic equilibrium conditions are studied within the framework of the density functional theory （DFT） , with the generalized gradient approximation （GGA） and the pseudopotential plane wave method. The results indicated that neither of BiTiO3 or BiVO3 is energetically stable under thermodynamic equilibrium conditions with respect to their competing phases, and approaches deviated from equilibrium are necessary to prepare these materials.