中文摘要：

稀土正铁氧体YFeO3呈正交钙钛矿结构，其晶体和纳米晶材料在电极材料、传感器和光催化领域具有重要的应用价值．用平面波赝势方法，采用广义梯度近似、改进的Perdew—Burke—Emzerhof交换-关联势、实空间超软赝势计算方案，研究了YFeO3晶体的几何结构、电子结构和光学性质．计算得到的晶格参量与报道的实验结果一致．通过对能带结构、态密度、介电函数、吸收系数和光电导率的计算和分析，确定YFeO3是直接能隙半导体，能隙最约为2．22eV,阐明了YFeOs晶体和纳米晶具有较好的可见光催化性能．

英文摘要：

Rare-earth orthoferrites （such as YFeO3） with orthorhombic perovskite-type structure are promising candidates in the fields of electrode materials, gas sensors and pbotocatalysts. The geometric structure, the electronic structure and the optical properties of YFeO3 crystal are investigated by using the plane-wave pseudo-potential method, with the scheme of generalized gradient approximation, revised Perdew-Burke-Emzerhof exchange-correlation potential and ultrasoft pseudopotential. The obtained lattice parameters are in good accordance with experimental results reported. The results confirm that YFeO3 crystal is a direct semiconductor with a gap （Eg） of about 2.22 eV, based on the analyses about band structure, density of state, dielectric function, absorption coefficient, and photoconductivity. It is clarified that YFeO3 crystal and nanocrystalline possess good photocatalytic activities for visible light.