CO dimer: new potential energy surface and rovibrational calculations
Richard Dawes1, Xiao-Gang Wang, Tucker Carrington
1Department of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, USA. dawesr@mst.edu
The Journal of Physical Chemistry. A
|June 7, 2013
Summary
Investigating the carbon monoxide (CO) dimer spectrum, this study developed an accurate potential energy surface (PES) using advanced ab initio methods. The new PES accurately predicts rovibrational energy levels, revealing new spectral features.
Area of Science:
- Computational Chemistry
- Molecular Spectroscopy
- Quantum Mechanics
Background:
- The carbon monoxide (CO) dimer presents a challenge for accurate theoretical description due to its complex potential energy surface.
- Previous ab initio studies have struggled to precisely model the rovibrational spectrum of the CO dimer.
Purpose of the Study:
- To develop a highly accurate potential energy surface (PES) for the CO dimer using advanced quantum chemical calculations.
- To investigate and predict the rovibrational spectrum of the CO dimer by solving the Schrödinger equation on the new PES.
- To assess the performance of different ab initio methods for describing intermolecular interactions in the CO dimer.
Main Methods:
- Construction of a new 4D global ab initio potential energy surface (PES) using coupled-cluster theory and an interpolating moving least-squares fitting procedure.
- Solving the rovibrational Schrödinger equation using a Lanczos algorithm.
- Utilizing explicitly correlated coupled-cluster methods (CCSD(T)-F12b) and core-electron correlation for improved accuracy.
Main Results:
- The developed PES yields excellent agreement with experimental rovibrational energy levels, achieving a root-mean-square (rms) fitting error of less than 0.1 cm⁻¹.
- The calculated spectrum shows an rms error of only 0.29 cm⁻¹ for 68 energy levels with rotational quantum number J ≤ 6.
- Identification of new energy level stacks, including a potentially observable low-lying stack labeled 'y1'.
Conclusions:
- The study successfully developed an accurate PES for the CO dimer, overcoming previous theoretical limitations.
- Advanced ab initio methods, particularly CCSD(T)-F12b with core-electron correlation, are crucial for accurate spectral predictions.
- The findings provide a reliable theoretical framework for understanding CO dimer spectroscopy and may lead to the observation of new spectral features.
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