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首页> 外文期刊>The Journal of Chemical Physics >A COUPLED CLUSTER STUDY OF THE STRUCTURES, SPECTROSCOPIC PROPERTIES, AND ISOMERIZATION PATH OF NCS- AND CNS-
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A COUPLED CLUSTER STUDY OF THE STRUCTURES, SPECTROSCOPIC PROPERTIES, AND ISOMERIZATION PATH OF NCS- AND CNS-

机译：NCS-和CNS-的结构，光谱性质和异构化路径的耦合聚类研究

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Three-dimensional near-equilibrium potential energy surfaces and dipole moment functions have been calculated for the X (1) Sigma(+) ground states of NCS- and CNS-, using the coupled cluster method with single and double substitutions augmented by a perturbative estimate of triple excitations [CCSD(T)] with a set of 154 contracted Gaussian-type orbitals. The corresponding equilibrium bond lengths at their linear geometries are r(e)(NC)=1.1788 Angstrom and r(e)(CS)=1.6737 Angstrom for NCS-, and r(e)(CN)=1.1805 Angstrom and r(e)(NS)=1.6874 Angstrom for CNS-. The predicted equilibrium rotational constants B-e of NCS- and CNS- are 5918.2 and 6282.7 MHz, respectively. The former agrees very well with the known experimental value (5919.0 MHz). Full three-dimensional variational calculations have also been carried out using the CCSD(T) potential energy and dipole moment functions to determine the rovibrational energy levels and dipole moment matrix elements for both NCS- and CNS-. The corresponding fundamental band origins (cm(-1)) nu(1), nu(2), and nu(3) and their absolute intensities (km/mol) at the CCSD(T) level are 2060.9/306.1, 451.5/2.2, and 707.5/12.8, respectively, for NCS- and 2011.4/6.6, 343.7/2.3, and 624.9/0.2 for CNS-. The calculated nu(1) (CN stretching) value for NCS- is in very good agreement with the experimental result, 2065.9 cm(-1). The calculated dipole moments of NCS- and CNS- in their ground vibrational states are 1.427 and 1.347 D, respectively The transition state geometry (saddle point) for the isomerization of NCS--->CNS- is predicted at the CCSD(T) level to be r(NC)=1.2044 Angstrom, R(CS)=1.9411 Angstrom and theta(angle NCS)=86.8 degrees. Its calculated energy is 62.6 and 26.5 kcal/mol above the minima of NCS- and CNS-, respectively, including zero-point energy corrections. The structure of the NCS radical was also optimized at the same level of theory, yielding ion to neutral bond length shifts in excellent agreement with those derived from recent photoelectron spectroscopy experiments. (C) 1995 American Institute of Physics. [References: 34]
机译：使用耦合簇方法，通过单扰和双扰替换，通过扰动估计增强了NCS-和CNS-的X（1）Sigma（+）基态的三维近平衡势能面和偶极矩函数。一组154个压缩高斯型轨道的三次激发[CCSD（T）]。对于NCS-，在其线性几何形状处相应的平衡键长度为r（e）（NC）= 1.1788埃和r（e）（CS）= 1.6737埃，以及r（e）（CN）= 1.1805埃和r（e对于CNS-）（NS）＝ 1.6874埃。 NCS-和CNS-的预测平衡旋转常数B-e分别为5918.2和6282.7 MHz。前者与已知的实验值（5919.0 MHz）非常吻合。还使用CCSD（T）势能和偶极矩函数进行了完整的三维变分计算，以确定NCS-和CNS-的旋转能级和偶极矩矩阵元素。对应的基带起点（cm（-1））nu（1），nu（2）和nu（3）及其在CCSD（T）水平的绝对强度（km / mol）为2060.9 / 306.1、451.5 /对于NCS-，分别为2.2和707.5 / 12.8，对于CNS-，分别为2011.4 / 6.6、343.7 / 2.3和624.9 / 0.2。计算得出的NCS-的nu（1）（CN拉伸）值与实验结果2065.9 cm（-1）非常吻合。 NCS-和CNS-在其地面振动状态下计算出的偶极矩分别为1.427和1.347D。NCS ---> CNS-异构化的过渡态几何构型（鞍点）预计在CCSD（T）级为r（NC）= 1.2044埃，R（CS）= 1.9411埃和theta（角度NCS）= 86.8度。其计算出的能量分别比NCS和CNS的最小值高62.6 kcal / mol和26.5 kcal / mol，其中包括零点能量校正。 NCS自由基的结构也以相同的理论水平进行了优化，产生的离子到中性键长的变化与最近的光电子能谱实验得出的结果非常吻合。 （C）1995年美国物理研究所。 [参考：34]

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