Special attention in the role of convection in vapor crystal growth has been paid since some single crystals under microgravity environments less than 1 g 0 exhibits a diffusive-convection mode and much uniformity in front of the crystal regions than a normal gravity acceleration of 1 g 0 . The total molar fluxes show asymmetrical patterns in interfacial distribution, which indicates the occurrence of either one single or more than one convective cell. As the gravitational level decreases form 1 g 0 down to 1.0 × 10 −4 g 0 , the intensity of convection, indicative of the maximum molar fluxes, is reduced significantly for ∆T = 30 K and 90 K. The total molar fluxes decay first order exponentially with the partial pressure of component B, PB (Torr) for 20 Torr ≤ P B ≤ 300 Torr, and two gravity accelerations of g y = 1 g 0 and 0.1 g 0 .

The convective flow structures in the vapor phase on earth are shown to be single unicellular, indicating the solutally dominant convection is important. These findings reflect that the total molar fluxes show asymmetrical patterns in a viewpoint of interfacial distributions. With decreasing the gravitational level form 1 g 0 down to 1.0 × 10 -4 g 0 , the total molar fluxes decay first order exponentially. It is also found that the total molar fluxes decay first order exponentially with increasing the partial pressure of component B, PB (Torr) form 5 Torr up to 400 Torr. Under microgravity environments less than 1 g 0 , a diffusive-convection mode is dominant and, results in much uniformity in front of the crystal regions in comparisons with a normal gravity acceleration of 1 g 0 . ated with the total molar flux along the crystal interfacial positions. Unless the two components have molecular weights very close to each other, it is concluded that for 2 ≤ M B ≤ 50, the dominant mode of convection is solutal. For the range of 5 Torr ≤ P B ≤ 100 Torr, the molar fluxes drop significantly, and, for 100 Torr ≤ P B ≤ 400 Torr, decreases slowly, and, for 5 Torr ≤ P B ≤ 400 Torr, the total molar fluxes decay first order exponentially with the partial pressure of component B, PB. ACKNOWLEDGEMENT