Langevin molecular dynamics of interfaces: Nucleation versus spiral growth

A simulation of surface growth is reported that directly introduces dynamics and thermal noise within a classical Langevin molecular-dynamics scheme. Using recent advances in massively parallel computation, extensive simulations on large two-dimensional lattices are possible. Surface growth is modeled by a dynamic solid-on-solid model, analogous to a discrete two-dimensional sine-Gordon equation. The influence of both homogeneous (thermal) nucleation and Frank-Read sources of spiral growth patterns are incorporated and compared. A phase diagram is described in the space of temperature and chemical potential difference between surface and vapor. At sufficiently high temperatures, a surface-roughening transition occurs. Finally, the same model is applied to other two-dimensional contexts: charge-density-wave materials in an electric field, and a two-dimensional Josephson junction in a perpendicular current.