Ionization potentials for the H₂CO trimer

Area of Science:

• Computational chemistry
• Quantum chemistry
• Molecular physics

Background:

• Formaldehyde (H2CO) is a fundamental molecule with significant chemical relevance.
• Understanding the electronic properties of formaldehyde clusters is crucial for various chemical processes.
• Ionization potentials (IPs) provide key insights into molecular electronic structure and stability.

Purpose of the Study:

• To computationally determine the lowest-lying vertical ionization potentials (IPs) of the formaldehyde trimer ((H2CO)3).
• To establish accurate theoretical values for (H2CO)3 IPs to guide future experimental and computational research.
• To investigate the influence of molecular conformation on the ionization potentials of the formaldehyde trimer.

Main Methods:

• Utilized the equation-of-motion ionization potential coupled-cluster with single and double excitations (EOM-IP-CCSD) method.
• Employed correlation consistent basis sets (aug-cc-pVnZ and aug-cc-pCVnZ, n=D, T) extrapolated to the complete basis set (CBS) limit.
• Applied the Feller-Peterson-Dixon (FPD) composite approach, considering core electron correlation effects and eight distinct (H2CO)3 conformations.

Main Results:

• Calculated twelve lowest-lying vertical IPs for the formaldehyde trimer.
• Observed a systematic decrease in IPs with increasing molecular size: IP(monomer) > IP(dimer) > IP(trimer).
• Found that the specific conformation of the trimer had a minor impact on the calculated ionization potentials.

Conclusions:

• Provided the first accurate computational ionization potential data for the formaldehyde trimer.
• The results suggest that electronic properties like IPs are sensitive to the degree of molecular aggregation.
• The study encourages further experimental (e.g., photoionization) and theoretical investigations of formaldehyde clusters.