skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Potential energy surface for C2H4I2+ dissociation including spin-orbit effects

Abstract

Previous experiments [Baer, et al. J. Phys. Chem. A 116, 2833 (2012)] have studied the dissociation of 1,2-diiodoethane radical cation (C2H4I2+•) and found a one-dimensional distribution of translational energy; an odd finding considering most product relative translational energy distributions are two-dimensional. The goal of this study is to obtain an accurate understanding of the potential energy surface (PES) topology for the unimolecular decomposition reaction C2H4I2+• - C2H4I+ + I•. This is done through comparison of many single-reference electronic structure methods, coupled-cluster single point (energy) calculations, and multi-reference calculations used to quantify spin-orbit (SO) coupling effects. We find that the structure of the C2H4I2+• reactant has a substantial effect on the role of SO coupling on the reaction energy. Both the BHandH and MP2 theories with an ECP/6-31++G** basis set, and without SO coupling corrections, provide accurate models for the reaction energetics. MP2 theory gives an unsymmetric structure with different C-I bond lengths, resulting in a SO energy for C2H4I2+• similar to that for the product I-atom and a negligible SO correction to the reaction energy. In contrast, DFT gives a symmetric structure for C2H4I2+•, similar to that of the neutral C2H4I2 parent, resulting in a substantial SO correction and increasingmore » the reaction energy by 6.0-6.5 kcal/mol. Also, we find that for this system single point energy calculations are inaccurate, since a small change in geometry can lead to a large change in energy.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1054463
Report Number(s):
PNNL-SA-89219
26690; KP1704020
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Molecular Physics, 110(19-20):2599-2609
Additional Journal Information:
Journal Name: Molecular Physics, 110(19-20):2599-2609
Country of Publication:
United States
Language:
English
Subject:
Electronic structure theory; density functional theory; spin-orbit coupling; unimolecular dissociation; chemical dynamics; Environmental Molecular Sciences Laboratory

Citation Formats

Siebert, Matthew R., Aquino, Adelia J., De Jong, Wibe A., Granucci, Giovanni, and Hase, William L. Potential energy surface for C2H4I2+ dissociation including spin-orbit effects. United States: N. p., 2012. Web. doi:10.1080/00268976.2012.725137.
Siebert, Matthew R., Aquino, Adelia J., De Jong, Wibe A., Granucci, Giovanni, & Hase, William L. Potential energy surface for C2H4I2+ dissociation including spin-orbit effects. United States. doi:10.1080/00268976.2012.725137.
Siebert, Matthew R., Aquino, Adelia J., De Jong, Wibe A., Granucci, Giovanni, and Hase, William L. Wed . "Potential energy surface for C2H4I2+ dissociation including spin-orbit effects". United States. doi:10.1080/00268976.2012.725137.
@article{osti_1054463,
title = {Potential energy surface for C2H4I2+ dissociation including spin-orbit effects},
author = {Siebert, Matthew R. and Aquino, Adelia J. and De Jong, Wibe A. and Granucci, Giovanni and Hase, William L.},
abstractNote = {Previous experiments [Baer, et al. J. Phys. Chem. A 116, 2833 (2012)] have studied the dissociation of 1,2-diiodoethane radical cation (C2H4I2+•) and found a one-dimensional distribution of translational energy; an odd finding considering most product relative translational energy distributions are two-dimensional. The goal of this study is to obtain an accurate understanding of the potential energy surface (PES) topology for the unimolecular decomposition reaction C2H4I2+• - C2H4I+ + I•. This is done through comparison of many single-reference electronic structure methods, coupled-cluster single point (energy) calculations, and multi-reference calculations used to quantify spin-orbit (SO) coupling effects. We find that the structure of the C2H4I2+• reactant has a substantial effect on the role of SO coupling on the reaction energy. Both the BHandH and MP2 theories with an ECP/6-31++G** basis set, and without SO coupling corrections, provide accurate models for the reaction energetics. MP2 theory gives an unsymmetric structure with different C-I bond lengths, resulting in a SO energy for C2H4I2+• similar to that for the product I-atom and a negligible SO correction to the reaction energy. In contrast, DFT gives a symmetric structure for C2H4I2+•, similar to that of the neutral C2H4I2 parent, resulting in a substantial SO correction and increasing the reaction energy by 6.0-6.5 kcal/mol. Also, we find that for this system single point energy calculations are inaccurate, since a small change in geometry can lead to a large change in energy.},
doi = {10.1080/00268976.2012.725137},
journal = {Molecular Physics, 110(19-20):2599-2609},
number = ,
volume = ,
place = {United States},
year = {2012},
month = {10}
}