Atomic investigation of steady-state dendrite tips by using phase-field crystal method

Steady-state dendrite growth is controlled by the states of dendrite tips, thus the morphology and growth kinetics of dendrite tip have always been a highly-studied issue in the field of dendrite growth. A crucial problem is to find out the factors influencing the morphology of dendrite tip, and to clarify their working mechanism. Since dendrite tip is at micrometer or even atomic scale, interface energy may probably plays an important role during the formation and stabilization of dendrite tips. Investigations of this issue at atomic scale is of significant because it can help us to clearly observe the morphology evolution of dendrite tip fundamentally, and specifically reveal the relationship between interface energy anisotropy and dendrite tip morphology. We investigate growth kinetics and morphology of dendrite tips at atomic scale by using phase-field crystal simulation. Atomic scale steady-state dendrite tips are obtained at different interface energy anisotropy and growth driving force. It is shown that the morphology of the forefront of dendrite tip varies periodically with time, which is related to the behavior of atom attachment during the steady-state growth of dendrite tip. Moreover, we demonstrate that growth driving force determines the overall shape of dendrite tip, but exerts little influence on the morphology of the forefront of dendrite tip which actually is determined by interface energy anisotropy. The dendrite tip of high interface energy anisotropy often presents sharp shape which is in favour of the formation of dendrite tip. Nevertheless, the shape of dendrite tip approaches to circle with decreasing magnitude of interface energy anisotropy, indicating that it is more difficult for the formation of dendrite tip under the circumstance of lower interface energy anisotropy.