Application of Multiconfiguration Pair-Density Functional Theory to the Diels–Alder Reaction
Application of Multiconfiguration Pair-Density Functional Theory to the Diels–Alder Reaction
复制标题
多构型对密度泛函理论在Diels-Alder反应中的应用
DOI：
10.1021/acs.jpca.2c06433
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Truhlar, Donald G.
中科院分区：
文献类型：
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作者：
Mitchell, Erica C.;Scott, Thais R.;Bao, Jie J.;Truhlar, Donald G.
Diels-Alder反应的过渡态是强相关的，从高到非常高的M诊断证明了这一点，因此它们需要用多参考方法来处理。多组态对密度泛函理论(MC-PDFT)将多组态波函数与电子密度和顶部对密度的泛函结合起来，以比不使用密度泛函的波函数方法低得多的成本计算了强关联体系的电子能量。本文将MC-PDFT应用于1，3-丁二烯与乙烯的Diels-Alder环加成反应，研究了两种反应路径：协同同步路径和双自由基步加成路径。现在已知最低能量的反应路径是协调同步的，而一种方法预测这一点的能力是一个重要的测试。通过与文献中已有的最好的理论结果的比较，我们测试了MC-PDFT的精度，并对两条路径上的稳定结构的几何构型和热焓以及过渡态的几何构型选择了几种顶端泛函。我们还计算了这两种路径的Arrhenius活化能，并将其与实验进行了比较。我们还与选择交换相关泛函的Kohn-Sham密度泛函理论(KS-DFT)进行了比较。CAS-PDFT给出了协调机制和分步机制的一致良好的能量和几何构型，但没有一个KS-DFT泛函给出了这两种机制的精确激活能。阶跃过渡态具有很强的关联性，MC-PDFT可以处理它，但KS-DFT(涉及单组态处理)误差较大。结果表明，对强关联过渡态采用多组态参考函数可以显著提高计算的可靠性，并且MC-PDFT可以以比竞争的多参考方法低得多的计算代价提供良好的精度。
Transition states for Diels–Alder reactions are strongly correlated, as evidenced by high-to-very-high M diagnostics, and therefore they require treatment by multireference methods. Multiconfiguration pair-density functional theory (MC-PDFT) combines a multiconfiguration wave function with a functional of the electron density and the on-top pair density to calculate the electronic energy for strongly correlated systems at a much lower cost than wave function methods that do not employ density functionals. Here we apply MC-PDFT to the Diels–Alder cycloaddition reaction of 1,3-butadiene with ethylene, where two kinds of reaction paths have been widely studied: concerted synchronous paths and diradical stepwise paths. The lowest-energy reaction path is now known to be a concerted synchronous one, and a method’s ability to predict this is an important test. By comparison to the best available theoretical results in the literature, we test the accuracy of MC-PDFT with several choices of on-top functional for geometries and enthalpies of stable structures along both paths and for the transition state geometries. We also calculate the Arrhenius activation energies for both paths and compare these to experiment. We also compare to Kohn–Sham density functional theory (KS-DFT) with selected exchange-correlation functionals. CAS-PDFT gives consistently good energies and geometries for both the concerted and stepwise mechanisms, but none of the KS-DFT functionals gives accurate activation energies for both. The stepwise transition state is very strongly correlated, and MC-PDFT can treat it, but KS-DFT (which involves a single-configuration treatment) has larger errors. The results confirm that using a multiconfigurational reference function for strongly correlated transition states can significantly improve the reliability and that MC-PDFT can provide good accuracy at a much lower computational cost than competing multireference methods.