Title: Association of Cl with C ₂ H ₂ by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Abstract

Barrierless unimolecular association reactions are prominent in atmospheric and combustion mechanisms but are challenging for both experiment and kinetics theory. A key datum for understanding the pressure dependence of association and dissociation reactions is the high-pressure limit, but this is often available experimentally only by extrapolation. Here we calculate the high-pressure limit for the addition of a chlorine atom to acetylene molecule (Cl + C₂H₂→C₂H₂Cl). This reaction has outer and inner transition states in series; the outer transition state is barrierless, and it is necessary to use different theoretical frameworks to treat the two kinds of transition state. Here we study the reaction in the high-pressure limit using multifaceted variable-reaction-coordinate variational transition-state theory (VRC-VTST) at the outer transition state and reaction-path variational transition state theory (RP-VTST) at the inner turning point; then we combine the results with the canonical unified statistical (CUS) theory. The calculations are based on a density functional validated against the W3X-L method, which is based on coupled cluster theory with single, double, and triple excitations and a quasiperturbative treatment of connected quadruple excitations [CCSDT(Q)], and the computed rate constants are in good agreement with some of the experimental results. The chlorovinyl (C₂H₂Cl) adduct has two isomersmore » that are equilibrium structures of a double-well C≡C–H bending potential. Two procedures are used to calculate the vibrational partition function of chlorovinyl; one treats the two isomers separately and the other solves the anharmonic energy levels of the double well. We use these results to calculate the standard-state free energy and equilibrium constant of the reaction.« less

Authors:

Zhang, Linyao  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-1848-8860"

Truhlar, Donald G.  ^[2];

• Search DOE PAGES for author "Truhlar, Donald G."
• Search DOE PAGES for ORCID "0000-0002-7742-7294"

Sun, Shaozeng  ^[3]

• Search DOE PAGES for author "Sun, Shaozeng"
• Search DOE PAGES for ORCID "0000-0003-2793-5925"

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+ Show Author Affiliations

1. School of Energy Science and Engineering, Harbin Institute of Technology, 150001 Harbin, People’s Republic of China,, Department of Chemistry, Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455,, Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455
2. Department of Chemistry, Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455,, Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455
3. School of Energy Science and Engineering, Harbin Institute of Technology, 150001 Harbin, People’s Republic of China,

Publication Date:

Mon Mar 02 00:00:00 EST 2020

Research Org.:

Univ. of New Mexico, Albuquerque, NM (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); China Scholarship Council; National Natural Science Foundation of China (NSFC)

OSTI Identifier:

1602557

Alternate Identifier(s):

OSTI ID: 1802801

Grant/Contract Number:  

SC0015997; 51536002; 201706120185

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 117 Journal Issue: 11; Journal ID: ISSN 0027-8424

Publisher:

Proceedings of the National Academy of Sciences

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; kinetics; transition state; rate constant; electronic structure; direct dynamics