While the issue of properly describing the out-of-plane bends (OPBs) in sp² hybridized carbon atoms has reappeared for c-SiC₂H₂, the present quantum chemical study provides a new characterization of this molecule in order to aid in its potential detection in astrophysically relevant studies. Combining the previous, high-level approach with MP2-F12/aug-cc-pVDZ gives exceptionally accurate results for the comparison of experimental rotational constants and seemingly reliable vibrational frequencies. Most notably, the brightest fundamental vibrational frequency in c-SiC₂H₂, the b₁ OPB, is predicted to lie at 673.4 cm⁻¹, within 4.0 cm⁻¹ of the previous matrix isolation experiment. As with c-C₃H₂, CCSD(T)-F12/aug-cc-pVTZ appears to be quite susceptible to over estimating the OPB anharmonic correction in c-SiC₂H₂ and may also do such for in-plane bends, as well. MP2-F12/aug-cc-pVDZ is less susceptible to these errors, and increasing the step size reduces this positive anharmonicity issue in both the cases. The OPB underestimation, however, likely still remains. Finally, estimates for some anharmonic vibrational frequencies are provided for the methylated form, c-SiC₂HCH₃, which is likely also a product of gas phase reactions of ·SiH with various alkynes.

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c-SiC2H2的振动分析：相关方法中面外弯曲问题的进一步证据

尽管对于c- SiC ₂ H ₂再次出现了正确描述sp ²杂化碳原子中的面外弯曲（OPB）的问题，但当前的量子化学研究提供了对该分子的新表征，以帮助其分子结构。天体相关研究中的潜在检测。将以前的高级方法与MP2-F12 / aug-cc-pVDZ结合使用，可以得到非常准确的结果，用于比较实验旋转常数和看似可靠的振动频率。最值得注意的是，在最亮的基本振动频率C-碳化硅₂ ħ ₂中，b ₁预测OPB位于673.4 cm ^-1处，在先前的基质分离实验的4.0 cm ^-1之内。与c- C ₃ H _2一样，CCSD（T）-F12 / aug-cc-pVTZ似乎很容易过高估计c- SiC ₂ H _2中的OPB非谐校正，并且也可能在平面内弯曲时如此，以及。MP2-F12 / aug-cc-pVDZ较不容易受到这些错误的影响，并且在两种情况下，增大步长都会减少这种积极的非谐性问题。然而，OPB仍可能被低估。最后，提供了甲基化形式c- SiC _2的一些非谐振动频率的估计值。HCH ₃，也可能是·SiH与各种炔烃气相反应的产物。