Advancing Machine-Learning Augmented Free-Energy Density Functionals for Fast and Accurate Quantum Simulations of Warm Dense Plasmas

密度泛函理论(DFT)是多体物理中最成功的方法之一，是理解自然界的物理和化学以及改善我们的日常生活的主要工具之一。DFT应用的例子从指导实验者发现近室温的超导体和其他功能材料，到控制化学反应以获得更好的产品，再到设计治疗疾病的药物。DFT的成功依赖于描述材料中电子如何相互作用的近似的准确性，即所谓的交换关联(XC)自由能密度泛函和无轨道DFT的非相互作用自由能泛函。在这个研究项目中，我们将开发基于机器学习的有限温度XC泛函和非相互作用自由能泛函，以显著提高密度泛函在等离子体物理和材料研究中的预测能力。这一研究项目的成果预计将在行星科学、天体物理、聚变能源和国防等各种科学领域和应用领域产生重大影响，并通过提供加速发现新材料的工具对社会产生积极影响。致密物质的压力从数百万到数千亿个大气层，广泛存在于宇宙中--从行星核和诸如棕矮星和白矮星的天体物理物体，到钻石-砧座-细胞压缩，再到实验室产生的冲击和惯性约束聚变内爆。要可靠地预测物质在这种极端条件下的静态、输运和光学性质，取决于第一性原理方法(如DFT)的准确性。该项目建立了一个研究计划，以提高极端材料量子模拟的DFT的精度和速度。该项目的目标包括：(1)开发用于从头算分子动力学模拟的完全热化和数值有效的XC自由能泛函；(2)通过开发一类新的无轨道(OF)无相互作用的自由能泛函，消除基于轨道的Mermin-Kohn-Sham(MKS)方案在高温下昂贵得令人望而却步的瓶颈；(3)利用这些发展，加上机器学习技术，使高效的-DFT实现能够加速电子结构计算，同时保持MKS的精度水平；以及(4)应用这些先进的工具来回答高能量密度等离子体物理和极端材料科学中的关键问题。该奖项由物理部的等离子体物理项目和材料研究部的凝聚态物质和材料理论项目共同支持。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Density-functional theory (DFT), one of the most successful methods in many-body physics, has been one of the main tools for understanding the physics and chemistry of nature as well as for improving our daily life. Examples of DFT applications range from guiding experimentalists to discover near-room-temperature superconductors and other functional materials, to controlling chemical reactions for better products, and to designing drugs to cure diseases. The success of DFT relies on the accuracy of approximations describing how electrons in a material interact with each other, the so-called exchange-correlation (XC) free-energy density functional and the non-interacting free-energy functional for orbital-free DFT. In this research project, finite-temperature XC-functionals and non-interacting free-energy functionals, advanced by machine learning, will be developed to significantly improve the predictive capability of DFT for both plasma physics and materials research. The outcome of this research project is expected to make significant impact in a variety of scientific fields and applications such as planetary science, astrophysics, fusion energy and national defense, as well as make a positive impact on the society through delivering tools to speed up discoveries of novel materials.Warm-dense matter, at pressures ranging from millions to hundreds of billions of atmospheres, exists vastly in the universe -- from planetary cores and astrophysical objects such as brown and white dwarfs, to diamond-anvil-cell compression, to shocks and inertial confinement fusion implosions created in a laboratory. Reliably predicting the static, transport and optical properties of matter at such extreme conditions depends on the accuracy of first-principles methods such as DFT. This project establishes a research program to improve the accuracy and speed of DFT for quantum simulations of extreme materials. The objectives of this project include: (1) developing fully thermalized and numerically efficient XC free-energy functionals for ab-initio molecular-dynamics simulations; (2) eliminating the prohibitively expensive bottleneck in the orbital-based Mermin-Kohn-Sham (MKS) scheme at elevated temperature by developing a novel class of orbital-free (OF) non-interacting free-energy functionals; (3) taking these developments, augmented with machine-learning techniques, to enable an efficient OF-DFT implementation for accelerating the electronic structure calculations that preserve the MKS level of accuracy; and (4) applying these advanced tools to answer key questions in high energy density plasma physics and in extreme materials science. This award is jointly supported by the Plasma Physics program in the Division of Physics and the Condensed Matter and Materials Theory program in the Division of Materials Research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.