Efficient Handling of Molecular Flexibility in Lattice Energy Minimization of Organic Crystals
Efficient Handling of Molecular Flexibility in Lattice Energy Minimization of Organic Crystals
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DOI：
10.1021/ct100597e
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发表时间：
2011-06-01
影响因子：
5.5
通讯作者：
Pantelides, C. C.
中科院分区：
文献类型：
--
作者：
Kazantsev, A. V.;Karamertzanis, P. G.;Pantelides, C. C.
针对柔性分子形成的晶体晶格能最小的问题，提出了一种新的算法--晶体优化器。该算法采用孤立分子量子力学(QM)计算晶格能量最小化过程中的分子内能量和构象相关的原子多极子。该算法通过使用局部近似模型(LAM)消除了在最小化的每一次迭代中执行QM计算的需要，并且对精度的影响最小。通过将晶格能量模型的QM派生分量存储在数据库中，并尽可能在后续计算中重复使用它们，实现了额外的计算效率。这使得该方法特别适合于涉及一系列晶格能量评估的应用，例如晶体结构预测。该算法能够有效地处理复杂系统，并具有相当大的构象灵活性。文中给出了算法的应用实例，范围从单组分晶体到具有数十个分子内自由度的共晶和柔性分子的盐，其最佳值由构象应变和堆积作用力的相互作用决定。对于任何给定的分子，要考虑的柔性程度可以从几个扭转角度到分子中存在的整个扭转角度、键角和键长的松弛。
This paper presents a novel algorithm, Crystal Optimizer, for the minimization of the lattice energy of crystals formed by flexible molecules. The algorithm employs isolated-molecule quantum mechanical (QM) calculations of the intramolecular energy and conformation-dependent atomic multipoles in the course of the lattice energy minimization. The algorithm eliminates the need to perform QM calculations at each iteration of the minimization by using Local Approximate Models (LAMs), with a minimal impact on accuracy. Additional computational efficiencies are achieved by storing QM-derived components of the lattice energy model in a database and reusing them in subsequent calculations whenever possible. This makes the approach particularly well suited to applications that involve a sequence of lattice energy evaluations, such as crystal structure prediction. The algorithm is capable of handling efficiently complex systems with considerable conformational flexibility. The paper presents examples of the algorithm's application ranging from single-component crystals to cocrystals and salts of flexible molecules with tens of intramolecular degrees of freedom whose optimal values are determined by the interplay of conformational strain and packing forces. For any given molecule, the degree of flexibility to be considered can vary from a few torsional angles to relaxation of the entire set of torsion angles, bond angles, and bond lengths present in the molecule.