Prof. Da-Dong YAN（严大东教授）

 Department of Physics Beijing Normal University

  Abstract: In the metastable system the phase transition is triggered by the critical nucleus. It has been well studied that nonclassical critical nucleus is not a drop of stable bulk in core and wrapped with a sharp interface, but a diffuse structure with different morphology depending on the metastability of matrix. Thus forming a critical nucleus does not mean the appearance of a new phase. While the dynamics before the phase is born is unknown yet. The growing dynamics of an individual critical nucleus is addressed in the phase separation process of metastable polymer blends. The super-critical nuclei are prepared with self-consistent field theory thermodynamically in the entire metastable region. In succession the dynamic density functional calculations are performed to characterize the growing dynamics with external potential dynamics theory. The numerical results indicate that there are three domains in the metastable region of phase diagram due to the discrepancies of the growing behaviors. Near binodal curve the nucleus grows as a classical nucleus does. In the opposite near the spinodal curve the critical nucleus grows as an expanding ripple rather than inflating hard sphere.

Location: 606 Conference Room 
Date and Time: January 5, 2012  09:30 – 10:30 a.m.