TSSMM Home Page

July 6, 2021

Bo Yang, Laura Gagliardi, and Donald G. Truhlar
Department of Chemistry, Chemical Theory Center, and Minnesota
Supercomputing Institute
University of Minnesota, Minneapolis, Minnesota 55455

Program: version date: July 28, 2017
Most recent update of manual: July 6, 2021


TSSMM is a Perl script that interfaces with the Gaussian 09 program or the Gaussian 16 program for the purpose of locating the stationary points on the lowest spin-orbit coupled (mixed-spin) potential energy surface (PES) using the electronic structure methods that are available in the Gaussian program. The program uses the two-state spin-mixing model (TSSMM). The interface is based on the Gaussian External keywords. The spin-orbit coupling between two different spin states of the same geometry is incorporated into the geometry optimization by using a pre-defined coupling constant. The coupling constant can be chosen semiempirically to reproduce the multiplet splitting in the atom or monatomic ion, or it can be determined by any other means, such as by a time-dependent density-functional theory (TDDFT) or a CASSI calculation at a representative geometry along the reaction coordinate where the low- and high-spin surfaces are close in energy.


TSSMM - version 2017 is licensed under the Apache License, Version 2.0.
The manual of TSSMM - version 2017 is licensed under CC-BY-4.0.

Publications of results obtained with the TSSMM - version 2017 software should cite the program and/or the article describing the program.

No guarantee is made that this software is bug-free or suitable for specific applications, and no liability is accepted for any limitations in the mathematical methods and algorithms used within. No consulting or maintenance services are guaranteed or implied.

The use of the TSSMM - version 2017 implies acceptance of the terms of the licenses. The software may be downloaded here.


B. Yang, L. Gagliardi, and D. G. Truhlar, TSSMM - version 2017, University of Minnesota, Minneapolis, MN, 2017. https://comp.chem.umn.edu/tssmm

"Transition States of Spin-Forbidden Reactions," B. Yang, L. Gagliardi, and D. G. Truhlar, Physical Chemistry Chemical Physics 20, 4129-4136 (2018). doi.org/10.1039/C7CP07227A


The manual is included as a pdf file in the tar file of the software. Or it can be downloaded as a separate file here.


Donald G. Truhlar's Home Page
Don Truhlar's software page
Computational Chemistry at the University of Minnesota
Minnesota Supercomputing Institute
Department of Chemistry at the University of Minnesota
This document last modified on July 12, 2021
Updated by:  Software Manager