Theoretical gravity studies on roles of convection in crystal growth of -Xe by physical vapor transport under normal and high gravity environments

Particular interest in the role of convection in vapor crystal growth has arisen since some single crystals under high gravity acceleration of $10g_0$ appear considerably larger than those under normal gravity acceleration ($1g_0$). For both ${\Delta}T=60\;K$ and 90 K, the mass flux increases by a factor of 3 with increasing the gravity acceleration from $1g_0$ up to $10g_0$. On the other hand, for ${\Delta}T=30\;K$, the flux is increased by a factor of 1.36 for the range of $1g_0{\leq}g{\leq}10g_0$. The maximum growth rates for $1g_0$, $4g_0$, $10g_0$ appear approximately in the neighborhood of y = 0.5, and the growth rates shows asymmetrical patterns, which indicate the occurrence of either one single or more than one convective cell. The maximum growth rate for $10g_0$ is nearly greater than that for $1g_0$ by a factor of 2.0 at $P_B=20\;Torr$. For three different gravity levels of $1g_0$, $4g_0$ and $10g_0$, the maximum growth rates are greater than the minimum rates by a factor of nearly 3.0, based on $P_B=20\;Torr$. The mass flux increases with increasing the gravity acceleration, for $1g_0{\leq}g_y{\leq}10g_0$, and decreases with increasing the partial pressure of component B, xenon (Xe), $P_B$. The $|U|_{max}$ is directly proportional to the gravity acceleration for $20\;Torr{\leq}P_B{\leq}300\;Torr$. As the partial pressure of $P_B$ (Torr) decreases from 300 Torr to 20 Torr, the slopes of the $|U|_{max}s$ versus the gravity accelerations increase from 0.1 sec to 0.17 sec. The mass flux of $Hg_2Cl_2$ is exponentially decayed with increasing the partial pressure of component B, $P_B$ (Torr) from 20 Torr up to 300 Torr.