中文摘要：

基于第一性原理研究了C原子在有无稀土La的奥氏体晶胞中扩散。计算结果表明，稀土加入后，产生了晶格畸变，晶胞体积增大，总能量略微升高；C原子易于沿着奥氏体晶胞的非密排晶面和密排晶向扩散；La的加入降低了C原子在奥氏体晶胞中的扩散激活能，且随着La和C浓度的降低，La使扩散激活能降低的幅度减小。研究了添加稀土使碳扩散加快的原因。

英文摘要：

This paper investigates the diffusion of carbon atoms in austenite cell with and without adding the rare earth lanthanum by CASTEP code based on first principles quantum mechanics theory. The calculated results show that the lattice presents distorting as adding lanthanum, and the the volume of cell increases, and the total energy rises appreciably. The carbon atoms tend to diffuse along the close-packed crystalline plane and the close-packed crystalline direction. The diffusion activation energy of carbon atoms in austenite cell can reduce as adding lanthanum and the amount falling diffusion activation energy decreases with reducing the concentration of lanthanum and carbon. It is reason that the diffusion of carbon is accelerated as adding rare earths.