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Published on: July 19, 2019
Multireference quantum Monte Carlo study of the O4 molecule
Michel Caffarel1, Ramón Hernández-Lamoneda, Anthony Scemama
1Laboratoire de Chimie et Physique Quantiques, CNRS-IRSAMC Université de Toulouse, France.
Fixed-node diffusion quantum Monte Carlo (FN-DMC) calculations determined the dissociation barrier and heat of formation for tetraoxygen. These accurate thermochemical energies are crucial for understanding tetraoxygen
Area of Science:
- Computational Chemistry
- Quantum Mechanics
- Theoretical Chemistry
Background:
- The chemical stability and reactivity of tetraoxygen (O4) remain subjects of interest.
- Accurate thermochemical data are essential for evaluating the role of O4 in chemical processes.
Purpose of the Study:
- To accurately determine the dissociation barrier of tetraoxygen (O4).
- To calculate the heat of formation for tetraoxygen (O4) relative to molecular oxygen.
- To provide reliable theoretical reference values for O4.
Main Methods:
- Fixed-node diffusion quantum Monte Carlo (FN-DMC) calculations.
- Utilized multireference trial wave functions constructed from truncated CASSCF(16,12).
- Employed a weight-consistent scheme to control fixed-node error.
Main Results:
- Calculated dissociation barrier: 11.6 ± 1.6 kcal/mol.
- Calculated heat of formation: 98.5 ± 1.9 kcal/mol.
- Results compared favorably with previous ab initio benchmark calculations (CASSCF-ACPF/AVQZ).
Conclusions:
- The obtained FN-DMC thermochemical energies represent highly accurate theoretical references for tetraoxygen.
- These values are critical for interpreting experimental observations and modeling atmospheric chemistry involving O4.
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