形核是一级不连续相变的起点，对后续材料组织的形成及最终产品的性能具有重要影响。形核过程、机制及其控制一直是材料科学和凝聚态物理等领域中最为活跃的研究课题之一。形核过程发生在原子空间尺度及扩散时间尺度，同时还具有随机性，因此充分认识形核过程将面临极大的挑战。受实验条件的限制，目前难以通过实验方法直接观测金属凝固中晶核的形成过程。近年来，随着计算材料科学的兴起，借助于数值模拟方法，凝固形核问题研究取得了很大的进展。本文首先回顾了形核理论的发展历程，然后对当前凝固形核模拟的研究进展进行述评，并介绍本课题组近年来基于晶体相场模型在形核研究方面的工作进展，最后对形核研究进行了展望。

Nucleation, the starting point of first-order discontinuous phase transformations, has long been an important issue in condensed matter physics and materials science. It plays a key role in determining the microstructures and mechanical properties of crystalline materials. As nucleation occurs at the atomic length scale and the diffusional time scale and is a typical stochastic event, investigating such kind of multiple scale issues will be taken up an enormous challenge. Because of the limitations of present experimental methods, it is still very hard to observe the nucleation process in situ. With the development of computational materials science, a deeper understanding of nucleation process has been obtained with the numerical modeling of nucleation process on the atomic scale. In this paper, some recent developments in modeling and simulation of nucleation process during solidification on the atomic scale are reviewed. Firstly, the development of classical nucleation theory and the step nucleation theory are reviewed. Then the developments in modeling of nucleation process by using the phase field method, Monte-Carlo method, Molecular dynamics method and the phase field crystal model are discussed. After that, some recent progresses in modeling of nucleation process during solidification in our research group by using the phase field crystal model are demonstrated. Finally, the outlooks of the future study on the nucleation during solidification are also presented.