Theoretical Studies of Intermolecular Forces

特拉华大学的Krzysztof Szalewicz教授获得了化学系化学理论、模型和计算方法项目的奖项，该项目研究分子之间的作用力。虽然这种力比作用在分子内部的化学键力弱十倍左右，但它们决定了大多数材料和生物体的性质。分子间力可以用Szalewicz和他的同事开发的方法来计算。与这种计算结果拟合的全局解析函数称为它的力场。一旦已知分子团簇、凝聚相或生物聚集体的力场，就可以通过求解原子运动的经典或量子方程来预测这些系统的所有特性。这项研究的一个目标是增加对这些特性对分子间力的依赖的理解，这为设计新材料提供了指导。另一个目标是改进算法和计算方法，以便对比现在可能大几倍的系统进行第一性原理预测。要计算的基于物理的力场有望改变生物分子模拟和材料建模与设计领域。这样的力场也与计量标准和解释光谱或散射测量有关，为构建大气模型提供数据，并有助于理解星际分子云的过程。新的晶体结构预测方法可以帮助制药行业发现药物的多态形式。Szalewicz研究的首要目标是增加基于第一性原理的对依赖于分子间力的物理、化学和生化现象的理解。高精度的分子间力场可以用对称自适应微扰理论（SAPT）计算，这是由Szalewicz的小组共同开发的。SAPT提供了一种独特的能力，根据导致静电、交换、感应和色散对相互作用能量贡献的四种基本物理机制来解释依赖于分子间力的性质。基于密度泛函理论（DFT）描述单体的SAPT，一种称为SAPT（DFT）的方法，与SAPT一样精确，但计算效率更高。理论的发展包括在DFT框架内预测准确色散能量的非局部相关泛函的工作，可以与准确色散能量配对的改进DFT方法，将Szalewicz小组早期开发的自动力场生成方法扩展到柔性单体，从第一原理预测晶体结构的多组分方法，以及基于从头开始计算单体性质的通用力场。朝着基于物理的生物分子力场的方向迈出了一步。这些方法在当前实验、观测或技术兴趣系统中的几种应用也被追求。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Professor Krzysztof Szalewicz of the University of Delaware is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to study forces acting between molecules. Although such forces are about ten times weaker than the chemical bonding forces acting inside molecules, they determine properties of most materials and living organisms. Intermolecular forces can be calculated using methods developed by Szalewicz and coworkers. A global analytic function fitted to results of such calculations is called its force field. Once the force field is known for a molecular cluster, condensed phase, or biological aggregate all properties of such systems can be predicted by solving the classical or quantum equations for atomic motions. One goal of this research is to increase the understanding of the dependence of these properties on specifics of intermolecular forces, which provides guidance in designing new materials. Another goal is to improve algorithms and computational methods to make first-principles predictions for systems several times larger than it is now possible. The physics-based force fields to be calculated hold promise for transforming the field of biomolecular simulations and of materials modelling and design. Such force fields are also relevant for metrology standards and for interpreting spectroscopic or scattering measurements, provide data for constructing models of the atmosphere, and help to understand processes in interstellar molecular clouds. The new crystal structure predictions methods can assist pharmaceutical industry in finding polymorphic forms of drugs.The overarching goal of Szalewicz's research is to increase the first-principles-based understanding of physical, chemical, and biochemical phenomena that depend on intermolecular forces. High-accuracy intermolecular force fields can be computed using symmetry-adapted perturbation theory (SAPT), which was co-developed by Szalewicz's group. SAPT provides a unique ability to interpret properties dependent on intermolecular forces in terms of the four fundamental physical mechanisms that lead to the electrostatic, exchange, induction, and dispersion contributions to the interaction energies. SAPT based on monomers described by density-functional theory (DFT), a method denoted as SAPT(DFT), is as accurate as SAPT, but computationally more efficient. The developments of theory include work on nonlocal correlation functionals which predict accurate dispersion energies within the DFT framework, improved DFT methods that can be paired with accurate dispersion energies, extensions of the automated force-field generation method developed earlier in Szalewicz's group to flexible monomers, multicomponent methods for crystal structure predictions from first principles, and universal force fields based on ab initio computed monomer properties, a step in the direction of physics-based biomolecular force fields. Several applications of these methods to systems of current experimental, observational, or technological interest are also pursued.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.