二氧化氮的低位四重态电子态

Low-lying quartet electronic states of nitrogen dioxide.

作者信息

Bera Partha P, Yamaguchi Yukio, Schaefer Henry F

机构信息

Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602-2525, USA.

出版信息

J Chem Phys. 2007 Nov 7;127(17):174303. doi: 10.1063/1.2780149.

DOI:10.1063/1.2780149

PMID:17994814

Abstract

The environmentally active molecule nitrogen dioxide (NO2) has been systematically studied using high level theoretical methods. The electronic ground state and the low-lying quartet states of NO2 have been investigated. Single reference restricted open-shell self-consistent field (SCF), complete active space SCF (CASSCF), spin-restricted (R) and spin-unrestricted (U) configuration interaction with single and double excitations (CISD), coupled cluster with single and double excitations (CCSD), CCSD with perturbative triple excitations [CCSD(T)], and internally contracted multireference configuration interaction (ICMRCI) methods along with Dunning's correlation consistent polarized valence cc-pVXZ and augmented cc-pVXZ (where X=T,Q,5) basis sets were used in this research. At the aug-cc-pV5Z/UCCSD(T) level the classical adiabatic excitation energies (Te values) of the three lowest-lying quartet excited states were predicted to be 83.3 kcalmol (3.61 eV, 29 200 cm(-1)) for the ã 4A2 state, 93.3 kcalmol (4.05 eV, 32 600 cm(-1)) for the b 4B2 state, and 100.8 kcalmol (4.37 eV, 35 300 cm(-1)) for the c 4A1 state. The quantum mechanical excitation energies (T 0 values) were determined to be 81.6 kcalmol (3.54 eV, 28 500 cm(-1)) for the a 4A2 state and 90.7 kcalmol (3.93 eV, 31 700 cm(-1)) for the b 4B2 state. The lowest quartet linear Renner-Teller 4Pi state gives rise to the a 4A2 state with 112.8 degrees and the b 4B2 state with 124.4 degrees <(ONO) bond angles upon bending. The b state shows some peculiar behavior. Although CASSCF, RCISD, UCISD, RCCSD, UCCSD, and RCCSD(T) methods predicted the presence of a Cs equilibrium geometry (a double minimum 4A' state), SCF, UCCSD(T), and ICMRCI wave functions predicted the C2v structure for the b 4B2 state. The importance of both dynamical and nondynamical correlation treatments for the energy difference between C2v and Cs structures of b state is highlighted in this context. The c 4A1 state is predicted to have a very small bond angle of 85.8 degrees . Potential energy diagrams with respect to the bond angles of the ground state and four quartet states are presented.

摘要

利用高水平理论方法对环境活性分子二氧化氮（NO₂）进行了系统研究。研究了NO₂的电子基态和低激发四重态。采用了单参考受限开壳自洽场（SCF）、完全活性空间SCF（CASSCF）、自旋受限（R）和自旋 unrestricted（U）的单双激发组态相互作用（CISD）、单双激发耦合簇（CCSD）、含微扰三重激发的CCSD[CCSD(T)]以及内收缩多参考组态相互作用（ICMRCI）方法，并结合了邓宁的相关一致极化价cc-pVXZ和扩展cc-pVXZ（其中X=T、Q、5）基组。在aug-cc-pV5Z/UCCSD(T)水平下，预测三个最低激发四重态的经典绝热激发能（Te值），对于ã ⁴A₂态为83.3 kcal/mol（3.61 eV，29200 cm⁻¹），对于b ⁴B₂态为93.3 kcal/mol（4.05 eV，32600 cm⁻¹），对于c ⁴A₁态为100.8 kcal/mol（4.37 eV，35300 cm⁻¹）。量子力学激发能（T₀值）对于a ⁴A₂态确定为81.6 kcal/mol（3.54 eV，28500 cm⁻¹），对于b ⁴B₂态为90.7 kcal/mol（3.93 eV，31700 cm⁻¹）。最低的四重态线性伦纳 - 泰勒4Pi态在弯曲时产生键角为112.8度的a ⁴A₂态和键角为124.4度的b ⁴B₂态<(ONO)。b态表现出一些特殊行为。尽管CASSCF（耦合簇单双激发）、RCISD（单双激发组态相互作用）、UCISD（单双激发组态相互作用）、RCCSD（单双激发耦合簇）、UCCSD（单双激发耦合簇）和RCCSD(T)方法预测存在Cs平衡几何结构（双极小值4A'态），但SCF（自洽场）、UCCSD(T)和ICMRCI波函数预测b ⁴B₂态为C₂v结构。在此背景下强调了动力学和非动力学相关处理对于b态C₂v和Cs结构之间能量差的重要性。预测c ⁴A₁态具有非常小的85.8度键角。给出了关于基态和四个四重态键角的势能图。