Accurate theoretical characterization of dioxygen difluoride: a problem resolved

Area of Science:

• Quantum Chemistry
• Molecular Spectroscopy
• Computational Chemistry

Background:

• Dioxygen difluoride (O2F2) has historically presented challenges for accurate theoretical modeling.
• The difficulty in describing O2F2 stems from the flatness of its potential energy surfaces, particularly for OF bond stretching.
• Previous theoretical methods struggled to precisely locate the global minimum energy configuration of O2F2.

Purpose of the Study:

• To identify the underlying reasons for the historical difficulty in theoretically describing dioxygen difluoride.
• To accurately determine the global minimum and vibrationally averaged molecular parameters of O2F2.
• To simulate and assign the infrared (IR) and ultraviolet (UV) spectra of O2F2.

Main Methods:

• High-level coupled-cluster calculations, specifically CCSD(T)-F12/VTZ-F12, were employed.
• Ab initio theory was used to locate the global minimum of the O2F2 potential energy surface.
• Vibrationally averaged bond lengths were calculated and compared with experimental data.
• Infrared (IR) and Ultraviolet (UV) spectra were computationally simulated.

Main Results:

• The flatness of the OO and OF stretching potential energy curves was identified as the primary reason for past theoretical difficulties.
• The global minimum of O2F2 was successfully located using CCSD(T)-F12/VTZ-F12 calculations.
• Vibrationally averaged bond lengths obtained from the calculations show excellent agreement with experimental values (within 0.01 Å).
• Simulated IR and UV spectra closely match experimental observations, enabling the assignment of spectral transitions.

Conclusions:

• The accurate theoretical description of dioxygen difluoride is achievable through high-level ab initio methods that account for vibrational averaging.
• Vibrational averaging is essential for reproducing experimental bond lengths with high accuracy.
• The study successfully explains the observed IR and UV spectra of O2F2, validating the theoretical approach.