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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Homogeneous Ni catalysts for H_2 oxidation and production: An assessment of theoretical methods, from density functional theory to post hartree-fock correlated wave-function theory
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Homogeneous Ni catalysts for H_2 oxidation and production: An assessment of theoretical methods, from density functional theory to post hartree-fock correlated wave-function theory

机译：用于H_2氧化和生产的均相Ni催化剂：从密度泛函理论到后hartree-fock相关波函数理论的理论方法的评估

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摘要

A systematic assessment of theoretical methods applicable to the accurate characterization of catalytic cycles of homogeneous catalysts for H_2 oxidation and evolution is reported. The key elementary steps involve heterolytic cleavage of the H-H bond and formation/cleavage of Ni-H and N-H bonds. In the context of density functional theory (DFT), we investigated the use of functionals in the generalized gradient approximation (GGA) as well as hybrid functionals. We compared the results with wave-function theories based on perturbation theory (MP2 and MP4) and on coupled-cluster expansions [CCD, CCSD, and CCSD(T)]. Our findings indicate that DFT results based on Perdew correlation functionals are in semiquantitative agreement with the CCSD(T) results, with deviations of only a few kilocalories/mole. On the other hand, the B3LYP functional is not even in qualitative agreement with CCSD(T). Surprisingly, the MP2 results are found to be extremely poor, in particular for the diproton Ni(0) and dihydride Ni(IV) species on the reaction potential energy surface. The Hartree-Fock reference wave function in MP2 theory gives a poor reference state description for these states that are electron rich on Ni, giving rise to erroneous MP2 energies. We present a detailed potential-energy diagram for the oxidation of H_2 by these catalysts after accounting for the effects of solvation, as modeled by a polarizable continuum, and of free energy estimated at the harmonic level of theory.
机译：报道了适用于准确表征均相催化剂对H_2氧化和逸出的催化循环的理论方法的系统评估。关键的基本步骤涉及H-H键的杂合裂解以及Ni-H和N-H键的形成/裂解。在密度泛函理论（DFT）的背景下，我们研究了泛函梯度近似（GGA）中的泛函以及混合泛函的使用。我们将结果与基于微扰理论（MP2和MP4）以及耦合簇扩展[CCD，CCSD和CCSD（T）]的波函数理论进行了比较。我们的发现表明，基于Perdew相关函数的DFT结果与CCSD（T）结果处于半定量一致，偏差仅为几千卡/摩尔。另一方面，B3LYP的功能与CCSD（T）甚至没有定性的协议。出人意料的是，发现MP2结果极差，特别是对于反应势能表面上的双质子Ni（0）和二氢化物Ni（IV）物种。 MP2理论中的Hartree-Fock参考波函数对这些在Ni上富电子的状态给出了较差的参考状态描述，从而导致错误的MP2能量。在考虑了可极化连续体建模的溶剂化作用和理论谐波水平估计的自由能之后，我们给出了这些催化剂氧化H_2的详细势能图。

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