Abstract
New global potential energy surface for the ground electronic state of ozone is constructed at the complete basis set level of the multireference configuration interaction theory. A method of fitting the data points by analytical permutationally invariant polynomial function is adopted. A small set of 500 points is preoptimized using the old surface of ozone. In this procedure the positions of points in the configuration space are chosen such that the RMS deviation of the fit is minimized. New ab initio calculations are carried out at these points and are used to build new surface. Additional points are added to the vicinity of the minimum energy path in order to improve accuracy of the fit, particularly in the region where the surface of ozone exhibits a shallow van der Waals well. New surface can be used to study formation of ozone at thermal energies and its spectroscopy near the dissociation threshold.
Highlights
The global potential energy surface (PES) for the ground electronic state of ozone, O3 X −→ O 3P + O2 3Σ−g, (1)is 10 years old
Most popular version of that surface [3] an analytic correction function was added to the spline in order to (i) eliminate the barrier by taking into account the results of more accurate ab initio calculations [4, 5] carried out along the one-dimensional minimum energy path to dissociation (MEP) and (ii) make the surface deeper in order to reproduce experimental value of the dissociation energy available at that time [6], De = 1.132 eV
Even before we start the computationally expensive ab initio calculations, we do already have some preliminary information about the PES
Summary
The global potential energy surface (PES) for the ground electronic state of ozone, O3 X −→ O 3P + O2 3Σ−g ,. The vdW well is separated from the main well by a reef-like structure with top of the reef slightly below the dissociation threshold Accurate reproduction of these features by the fitting function is highly desirable, because they are expected to affect the dynamics and spectroscopy of ozone. We found that the fitting approach of Braams and Bowman [12] allows obtaining accurate representation of ozone PES with as few as 500–600 data points. If such small number of points is sufficient, the electronic structure calculations can be carried out at a very high level of theory, which offers a very attractive method of building accurate PES of ozone and other highly symmetric molecules.
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