本课题开发了高效的团簇全局最优结构搜索程序（Tsinghua Global Minimum, TGMin-3），可以用于加速搜索具有新奇结构和特殊性质的团簇，包括：金属团簇、非金属团簇、非金属掺杂金属的混合团簇；中性团簇、阳离子团簇和阴离子团簇；原子团簇、分子团簇和复合团簇等。在TGMin-3程序中，目前已经实现了几种改进后的算法，例如：随机扰动种子（RP）算法，盆地跳跃搜索（BH）算法，对称性结构生成（SS）算法，结构松弛预优化（GR）算法，相似度检测识别（SR）算法和平面度检测识别（PR）算法等。通过加入这些改进后的算法，使得TGMin-3程序能够更加高效地搜索团簇的全局最优结构。以金团簇Aun、硼团簇Bn、碳团簇Cn和水团簇(H2O)n等为例，研究了它们的结构演变规律。并结合光电子能谱和红外光谱等实验，验证了团簇全局和局部最优结构。通过对水团簇的结构搜素，我们发现：水团簇(H2O)n (n=3~5)最稳定的结构是平面环状结构， (H2O)6和 (H2O)8最稳定的结构分别是立体棱柱结构（prism）和立方结构（cube），(H2O)7则是“6+1”的立体棱柱变形结构，可以看作是 (H2O)6到(H2O)8的结构转变。除此之外，我们发现了水团簇五聚体 (H2O)5立体结构的存在，同时这也是水团簇从平面环状结构到立体三维结构的转折点，打破了人们对于平面环状水团簇的固有认识。对于水团簇八聚体，我们发现了(H2O)8 的五个立方体共存结构，点群分别是：D2d, S4, C2, C2 和 Ci，并研究了它们的热力学、动力学稳定性和异构化转变机理，计算了过渡态和转变活化能垒，发现这五个立方异构体都是可以稳定共存的。另外，我们发现了水团簇八聚体的手性异构体，点群为 C2。我们发现氢键网络的拓扑结构，对于稳定水八聚体的最小立方冰结构，具有至关重要的作用。为了解释水八聚体 (H2O)8 的稳定性，在前人已经提出氢键定义后，我们提出了氢键的3c-2e新模型，进一步完善了氢键的定义，解释了水八聚体的稳定性。本研究的新发现，对进一步研究水、冰的结构和性质，以及生命的起源等具有重要意义。

In this project, an efficient global minimum search for cluster program (TGMin-3) is developed, which can be used to accelerate the search for clusters with novel structures and special properties, including metal clusters, non-metal clusters and mixed clusters of non-metals doped metals; Neutral cluster, cationic cluster and anionic cluster; Atomic clusters, molecular clusters and composite clusters. In TGMin-3 program, several improved algorithms have been implemented, such as random disturbance seed (RP) algorithm, basin jump search (BH) algorithm, symmetrical structure generation (SS) algorithm, structural relaxation pre-optimization (GR) algorithm, similarity detection and recognition (SR) algorithm and flatness detection and recognition (PR) algorithm.By adding these improved algorithms, TGMin-3 program can search the global optimal structure of clusters more efficiently. Taking gold cluster, boron cluster, carbon cluster and water cluster as examples, their structural evolution laws were studied. Combined with photoelectron spectroscopy and infrared spectroscopy, the global and local optimal structures of clusters are verified. By searching the structure of water clusters, we found that the most stable structure of water clusters (H2O)n(n =3~5) is planar ring structure, (H2O)6 and (H2O)8 are prism and cube structure respectively, and (H2O)7 is a "6 + 1" solid prism deformation structure, which can be regarded as the structural transformation from (H2O)6 to (H2O)8.In addition, we found the existence of pentamer (H2O)5 three-dimensional structure, which is also the turning point of water clusters from planar ring structure to three-dimensional structure. We found five cubic coexistence structures of (H2O)8. Their thermodynamic and isomerization transformation mechanism are studied. It is found that these five cubic isomers can coexist stably. In addition, we found the chiral isomer of water octamer. The topology of hydrogen bond network plays an important role in stabilizing the cubic structure of water octamer. We also proposed a 3c-2e new model of hydrogen bond. The new findings of this study are of great significance to further study the structure and properties of water and ice and the origin of life.