Agrawal P M, Malshe M, Narulkar R, Raff L M, Hagan M, Bukkapatnum S, Komanduri R
Mechanical & Aerospace Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
J Phys Chem A. 2009 Feb 5;113(5):869-77. doi: 10.1021/jp8085232.
Previous methods proposed for obtaining analytic potential-energy surfaces (PES) from ab initio electronic structure calculations are not self-starting. They generally require that the sampling of configuration space important in the reaction dynamics of the process being investigated be initiated by using chemical intuition or a previously developed semiempirical potential-energy surface. When the system under investigation contains four or more atoms undergoing three- and four-center reactions in addition to bond scission processes, obtaining a sufficiently converged initial sampling can be very difficult due to the extremely large volume of configuration space that is important in the reaction dynamics. It is shown that by combining direct dynamics (DD) with previously reported molecular dynamics (MD), novelty sampling (NS), and neural network (NN) methods, an analytical surface suitable for MD computations for large systems may be obtained. Application of the method to the investigation of N-O bond scission and cis-trans isomerization reactions of HONO followed by comparison of the resulting neural network potential-energy surface to one obtained by using a semiempirical potential to initiate the sampling shows that the two potential surfaces are the same within the fitting accuracy of the surfaces. It is concluded that the combination of direct dynamics, molecular dynamics, novelty sampling, and neural network fitting provides a self-starting, robust, and accurate DD/MD/NS/NN method for the execution of first-principles, ab initio, molecular dynamics studies in systems containing four or more atoms which are undergoing simultaneous two-, three-, and four-center reactions.
先前提出的用于从从头算电子结构计算中获取解析势能面（PES）的方法并非自启动的。它们通常要求通过化学直觉或先前开发的半经验势能面来启动对所研究过程反应动力学中重要的构型空间的采样。当所研究的系统除键断裂过程外还包含四个或更多原子进行三中心和四中心反应时，由于反应动力学中重要的构型空间体积极大，要获得充分收敛的初始采样可能非常困难。结果表明，通过将直接动力学（DD）与先前报道的分子动力学（MD）、新颖采样（NS）和神经网络（NN）方法相结合，可以获得适用于大型系统MD计算的解析表面。将该方法应用于HONO的N - O键断裂和顺反异构化反应的研究，然后将所得神经网络势能面与使用半经验势能启动采样得到的势能面进行比较，结果表明在势能面的拟合精度范围内，这两个势能面是相同的。得出的结论是，直接动力学、分子动力学、新颖采样和神经网络拟合的结合为在包含四个或更多原子且同时进行双中心、三中心和四中心反应的系统中执行第一性原理、从头算分子动力学研究提供了一种自启动、稳健且准确的DD/MD/NS/NN方法。
