Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India.
Interdisciplinary Center of Molecular Materials (ICMM) and Computer-Chemistry-Center (CCC), Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße 25, 91052 Erlangen, Germany.
J Chem Phys. 2018 Oct 14;149(14):144113. doi: 10.1063/1.5049700.
Plane wave basis sets offer many advantages in molecular dynamics due to their efficiency and simplicity. In combination with hybrid density functionals, they become computationally expensive due to the evaluation of the Hartree-Fock exchange energy. The computational cost can be significantly reduced by screening the Kohn-Sham orbital products after localizing the orbitals in real space. However, such a procedure introduces apparent errors in the wavefunctions and nuclear forces resulting in unstable dynamics. It is shown here that a noise-stabilized dynamics approach can overcome this problem and at the same time permits using insufficiently converged wavefunctions for evaluating atomic forces. In this way, we achieve significant speed up even for a small system containing about 100 atoms. After benchmarking the accuracy and efficiency of this approach, we use it in combination with well-sliced metadynamics to compute the free energy barrier of formamide hydrolysis in alkaline aqueous medium. These results provide insight into the error of the Perdew-Burke-Ernzerhof functional in predicting the free energy barrier for hydrolysis reactions in water.
平面波基组由于其效率和简单性，在分子动力学中具有许多优势。与杂化密度泛函结合使用，由于 Hartree-Fock 交换能的评估，它们的计算成本变得非常高。通过在实空间中对轨道进行本地化后筛选 Kohn-Sham 轨道产物，可以显著降低计算成本。然而，这样的过程会导致波函数和核力出现明显的误差，从而导致动力学不稳定。本文表明，噪声稳定动力学方法可以克服这个问题，同时允许使用尚未充分收敛的波函数来评估原子力。通过这种方式，即使对于包含约 100 个原子的小系统，我们也可以实现显著的加速。在基准测试了这种方法的准确性和效率之后，我们将其与切片元动力学结合使用，以计算在碱性水介质中甲酰胺水解的自由能势垒。这些结果提供了对 Perdew-Burke-Ernzerhof 泛函在预测水中水解反应自由能势垒方面的误差的深入了解。
