为无序材料设计新型生成模型,实现高效热平衡采样。
Boltzmann generators for amorphous particle systems
- 将物理对称性嵌入黎曼随机插值,构建适配无序体系的生成模型。
- 实验表明引入对称性可显著提升采样精度,但连续流模型存在数值误差累积。
- 揭示连续流模型在统计力学中热力学一致性难以保持的根本缺陷。
热力学平衡下的系统构型采样是统计物理中的长期挑战。玻尔兹曼生成器通过生成模型提出独立构型,并利用精确似然评估进行重要性重加权。近期基于连续归一化流和流匹配的玻尔兹曼生成器在粒子系统和生物分子中取得显著进展,但尚未拓展至玻璃等无序材料,其平衡采样极为缓慢。由于无序结构导致的对称性和几何约束不同于晶体与生物分子,现有生成模型无法直接适用。本文通过将所需协变性直接嵌入黎曼随机插值,开发了专为无序材料设计的玻尔兹曼生成器框架。该框架利用协变图神经网络处理周期边界条件与粒子对称性。数值实验表明,强制物理对称性显著提升生成器精度,但也揭示连续流形式的固有局限:似然积分过程中的累积数值误差破坏时间反演对称性,损害精确热力学重加权。这一发现揭示了连续流生成模型在统计力学中的根本挑战,亟需保持精确热力学一致性的替代方案。
原文摘要 · Abstract (English)
Sampling configurations in thermodynamic equilibrium is a long-standing challenge in statistical physics. Boltzmann generators address this problem by employing generative models to propose independent configurations, which are then reweighted via importance sampling using exact likelihood evaluations. Recent Boltzmann Generators based on continuous normalizing flows and flow matching have achieved significant success for particle systems and biomolecules. However, these approaches have not been extended to amorphous materials (glasses), for which equilibrium sampling is notoriously slow. Because of their disordered structure, the invariances and geometrical constraints of amorphous materials differ from those of crystals and biomolecules, preventing the direct use of existing generative models. Here, we develop Boltzmann Generators tailored to amorphous materials by building the required equivariances directly into Riemannian stochastic interpolants. Our framework incorporates periodic boundary conditions and particle symmetries using equivariant graph neural networks. Numerical experiments demonstrate that enforcing physical symmetries significantly improves the accuracy of Boltzmann Generators, but also reveal an intrinsic limitation of the continuous-flow formulation: accumulated numerical errors during likelihood integration break time-reversibility, compromising exact thermodynamic reweighting. These results reveal a fundamental challenge for continuous-flow generative models in statistical mechanics and call for alternative approaches that preserve exact thermodynamic consistency.
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