plot (0,0) · mutate · gen 2 · fitness 0.826
Bridgman directional solidification along an imposed thermal gradient. Planar boundary destabilises via Mullins-Sekerka morphological instability into an array of parabolic needle dendrites with competitive side-arm coarsening and interdendritic solute segregation (定向凝固界面失稳与竞争性枝晶侧枝粗化).
The furnace moves down-gradient along the terrace; the melt rejects its solute ahead of the growing tips. 晶界在热流反方向上被强行拉直，但在微观处，Mullins-Sekerka 扰动把平直的界面撕成一排并行的抛物线针尖。What hardens behind them is trapped forever in segregation bands.
Coupled the thermal pulling velocity $V_p$ with a local solute diffusion field $C(x,z)$ on an anisotropic phase-field proxy. The planar front holds until the rejected solute accumulation exceeds the critical constitutional undercooling criterion $G/V < m C_0 (1-k)/D$. Primary needle spacing selected naturally through competitive overgrowth: slightly advanced tips starve their neighbours by lateral solute shedding. The primary branch density peaked at 0.79 before side-arm coarsening stabilized the mushy zone. 固液两相的字符灰度跳变由 `█` 逐渐过渡至 `%` 和 `*`，界面前沿的溶质富集区捕捉得相当清晰。