Description: A previously developed one-dimensional (ID) computational model for heat flow and nonequilibrium phase change phenomena induced by pulsed-laser irradiation has been extended to two-dimensions. The 2D modeling focuses attention on the heat flow from localized sources embedded in an otherwise planar matrix. For example, nucleation events occurring in undercooled liquids such as molten Si formed by pulsed-laser melting of amorphous Si (a-Si) and inhomogeneous absorption due to randomly occurring defects in targets used for pulsed-laser ablation can be treated. Concepts introduced in the ID modeling, such as the state diagram and the state array are extended to 2D and refined. As an example of the calculations that are now possible, the laser-induced formation and propagation of buried liquid layers are followed in two dimensions for the case of a-Si on a crystalline silicon substrate. It is demonstrated how solid phase growth from individual nucleation sites gives rise to a nearly planar liquid layer propagating through the a-Si. Another example briefly addresses questions related to the early stages of the laser ablation of insulators such as MgO, where it is believed that the absorption of the laser radiation occurs at localized but extended regions of high concentrations of defects. The 2-D program has been rewritten for massively parallel machines such as the Intel Paragons in ORNL`s Center for Computational Sciences by one of us (CLL), thus allowing larger and more accurate calculations for complex systems to be carried out in reasonable times.
Date: April 1995
Creator: Liu, C. L. & Wood, R. F.
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