An explicitly correlated six-dimensional potential energy surface for the SiCSi + H₂ complex.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• The SiCSi molecule is an interstellar species of interest.
• Understanding the interaction between SiCSi and H2 is important for astrochemistry.
• Accurate potential energy surfaces are essential for molecular dynamics simulations.

Purpose of the Study:

• To develop the first six-dimensional potential energy surface (PES) for the SiCSi + H2 system.
• To analyze the dependence of the PES on the bending angle.
• To compute the second virial coefficient for the SiCSi + H2 pair.

Main Methods:

• Ab initio calculations using the explicitly correlated coupled-cluster method with a triple zeta basis set (CCSD(T)-F12/aug-cc-pVTZ).
• Fitting of computed energies to an analytical function using spline, least-squares, and kernel-based methods.
• Calculation of the second virial coefficient using classical and semi-classical approaches.

Main Results:

• A six-dimensional PES for the SiCSi + H2 complex was successfully developed.
• Two minimums of comparable depths were identified at the equilibrium geometry of SiCSi.
• A reduced four-dimensional PES, averaged over H2 orientation, was also generated.
• The second virial coefficient was computed using the developed PES.

Conclusions:

• The developed PES provides an accurate representation of the SiCSi-H2 interaction.
• The study offers valuable data for theoretical studies of SiCSi-H2 systems.
• The computed second virial coefficient can be used to validate theoretical models and experiments.