Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dual-Level Approach to Instanton Theory   Instanton theory is an established method to calculate rate constants of
chemical reactions including atom tunneling. Technical and methodological
improvements increased its applicability. Still, a large number of energy and
gradient calculations is necessary to optimize the instanton tunneling path and
2$^{\text{nd}}$ derivatives of the potential energy along the tunneling path
have to be evaluated, restricting the range of suitable electronic structure
methods. To enhance the applicability of instanton theory, we present a
dual-level approach in which instanton optimizations and Hessian calculations
are performed using an efficient but approximate electronic structure method
and the potential energy along the tunneling path is recalculated using a more
accurate method. This procedure extends the applicability of instanton theory
to high-level electronic structure methods for which analytic gradients may not
be available, like local linear-scaling approaches. We demonstrate for the
analytical Eckart barrier and three molecular systems how the dual-level
instanton approach corrects for the largest part of the error caused by the
inaccuracy of the efficient electronic structure method. This reduces the error
of the calculated rate constants significantly.

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The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc