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Introduction

Kinisot is a Python program to compute kinetic isotope effects from two Gaussian output files, one of which is a ground state and the other a transition state. It is developed in the Paton research group at Colorado State University.

This is a Python version of Kinisot, inspired by the Fortran version originally written by Henry Rzepa. This version does not require parameter files to run and allows easy manipulation of temperature and vibrational scaling factors. The level of theory and basis set are detected from in the output files and the program will attempt to assign the appropriate scaling factor based on data from the Truhlar group. Isotopic substitutions are to be specified by the command line, such that separate computations with Gaussian are not required. The program diagonalizes the mass-weighted Hessian matricies to obtain harmonic vibrational frequencies and Bigeleisen-Mayer Reduced Isotopic Partition Function Ratios. One difference with the Gaussian program itself is that the lowest five/six normal modes (translations and rotations) are not projected out, however, this is also the approach taken by quiver. Testing this approach against calculation of the Reduced Isotopic Partition Function Ratios by hand (!) using the frequencies in the Gaussian output files led to agreeement up to 4DP. A one-dimensional tunneling correction is also included, which is the Bell infinite-parabola model.

Also see related discussions on computing KIE values

The current version is currently hard-coded to consider ²D/¹H, ¹³C/¹²C and ¹⁷O/¹⁶O isotopic replacements. This can be modified in Hess_to_Freq.py.

A video guide to using an older version this software is available at Youtube:

Installation

To install Kinisot with conda:

conda install kinisot -c conda-forge

To install Kinisot with pypi:

pip install kinisot

Usage

python -m kinisot --rct reactant_output --ts ts_output --iso 1,2,3 (-t temperature) (-s scalefactor)  

• The two output files contain Gaussian frequency calculations performed for the reactant and transition state at the same level of theory.
• The --iso flag is required and specifies a string of atom number(s) which are to be substituted for heavier isotopes. Multiple atom numbers require quotation marks and are separated by spaces.
• The -t option specifies temperature (in Kelvin). N.B. This does not have to correspond to the temperature used in the Gaussian calculation since the Reduced Isotopic Partition Function Ratios are evalulated at the requested temperature. The default value is 298.15 K.
• The -s option is a scaling factor for vibrational frequencies. Empirical scaling factors have been determined for several functional/basis set combinations, and these are applied automatically using values from the Truhlar group based on detection of the level of theory and basis set in the output files. The ZPE-scaling factors are selected if available. The default value when no scaling factor is available is 1 (no scale factor).

See examples/ for more examples