Atomic simulations using an embedded atom method (EAM) potential were performed to study changes of packing patts in titanium clusters containing tens to thousands of atoms.The findings revealed that the changes came from the movements and rearrangements of surface atoms in a large temperature range,and they were strongly dependent on cluster size and elevated temperatures.Small size clusters with icosahedron (Ih) configurations of geometric shell closures were preferred.As the cluster size increased,most of the atoms in these clusters could hold their HCP packing patts.With the increasing temperature,the coexistence of different packing patts including HCP,BCC,and Ih occurred.At a high temperature,the disorderly packing quickly extended into the entire region of a large size cluster.The calculations of specific heat were compared with Dulong-Petit law.The simulations provide the possibility to straddle structural transformations and determine critical size suitable for classical theory under certain thermal conditions.