PubMed Health⌕ Search

Biomedical subjects

Jean-Marc Debierre

Publications and source records attributed to Jean-Marc Debierre.

4 recordsLinked to original sources
PubMed2005

Growth patterns in a channel for singular surface energy: phase-field model.

We study solidification in a two-dimensional channel for faceted materials whose facets correspond to cusps in the gamma plot. The main result is the existence of three growth modes, according to the anisotropy strength: a single faceted finger at high anisotropies, two faceted fingers in the intermediate range, and an oscillating mode at low anisotropies. Simple geometrical and dynamical models are proposed to explain the nature of the observed modes. In particular, the one-finger patterns are shown to be similar to free dendrites while the two-finger patterns correspond to confined solidification fingers.

Journal Article↗
PubMed2003

Phase-field approach for faceted solidification.

We extend the phase-field approach to model the solidification of faceted materials. Our approach consists of using an approximate gamma plot with rounded cusps that can approach arbitrarily closely the true gamma plot with sharp cusps that correspond to faceted orientations. The phase-field equations are solved in the thin-interface limit with local equilibrium at the solid-liquid interface [A. Karma and W.-J. Rappel, Phys. Rev. E 53, R3017 (1996)]. The convergence of our approach is first demonstrated for equilibrium shapes. The growth of faceted needle crystals in an undercooled melt is then studied as a function of undercooling and the cusp amplitude delta for a gamma plot of the form gamma=gamma0[1+delta(/sin theta/+/cos theta/)]. The phase-field results are consistent with the scaling law Lambda approximately V(-1/2) observed experimentally, where Lambda is the facet length and V is the growth rate. In addition, the variation of V and Lambda with delta is found to be reasonably well predicted by an approximate sharp-interface analytical theory that includes capillary effects and assumes circular and parabolic forms for the front and trailing rough parts of the needle crystal, respectively.

Journal Article↗
PubMed2002

Measuring kinetic coefficients by molecular dynamics simulation of zone melting.

Molecular dynamics simulations are performed to measure the kinetic coefficient at the solid-liquid interface in pure gold. Results are obtained for the (111), (100), and (110) orientations. Both Au(100) and Au(110) are in reasonable agreement with the law proposed for collision-limited growth. For Au(111), stacking fault domains form, as first reported by Burke, Broughton, and Gilmer [J. Chem. Phys. 89, 1030 (1988)]. The consequence on the kinetics of this interface is dramatic: the measured kinetic coefficient is three times smaller than that predicted by collision-limited growth. Finally, crystallization and melting are found to be always asymmetrical and here again the effect is much more pronounced for the (111) orientation.

Journal Article↗