A fully ab initio quartic force field of spectroscopic quality for SO_3

Abstract

The quartic force field of SO${}_3$ was computed fully ab initio using coupled cluster (CCSD(T)) methods and basis sets of up to $spdfgh$ quality. The effect of inner-shell correlation was taken into account. The addition of tight $d$ functions is found to be essential for accurate geometries and harmonic frequencies. The equilibrium geometry and vibrational fundamentals are reproduced to within 0.0003 Åand (on average) 1.15 cm^{-1}, respectively. We recommend the following revised values for the harmonic frequencies: ${\omega }_1=1082.7,{\omega }_2=502.6,{\omega }_3=1415.4,{\omega }_4=534.0c{m}^{-1}$. In addition, we have shown that the addition of inner polarization functions to second-row elements is highly desirable even with more approximate methods like B3LYP, and greatly improves the quality of computed geometries and harmonic frequencies of second-row compounds at negligible extra computational cost. For larger such molecules, the B3LYP/VTZ+1 level of theory should be a very good compromise between accuracy and computational cost.

RevTeX, 22 pages; for special issue of Spectrochimica Acta A "Theoretical spectroscopy, state of the science" (eds. T. J. Lee, M. Head-Gordon)

Cited by in corpus (7)

• Development of Novel Density Functionals for Thermochemical Kinetics
• ExoMol molecular line lists - XIV: The rotation-vibration spectrum of hot SO${}_2$
• Anharmonic force field and vibrational frequencies of tetrafluoromethane (CF${}_4$) and tetrafluorosilane (SiF${}_4$)
• The heat of atomization of sulfur trioxide, SO${}_3$ - a benchmark for computational thermochemistry
• ExoMol molecular line lists - XVII The rotation-vibration spectrum of hot SO${}_3$
• An ab initio variationally computed room-temperature line list for SO3
• Anharmonic force fields of perchloric acid, HClO${}_4$, and perchloric anhydride, Cl${}_2$O${}_7$. An extreme case of inner polarization