Fit point-wise ab initio calculation potential energies to a multi-dimension morse/long-range model

Zhai, Yu

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https://hdl.handle.net/2142/91111 Copy

Description

Title

Fit point-wise ab initio calculation potential energies to a multi-dimension morse/long-range model

Author(s)

Zhai, Yu

Contributor(s)

• Le Roy, Robert J.
• Li, Hui

Issue Date

2016-06-20

Keyword(s)

Spectroscopy of Large Amplitude Motions

Abstract

• \begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.35]{mdmlr.eps} \end{wrapfigure} A potential energy surface (PES) is a fundamental tool and source of understanding for theoretical spectroscopy and for dynamical simulations. Making correct assignments for high-resolution rovibrational spectra of floppy polyatomic and van der Waals molecules often relies heavily on predictions generated from a high quality {\it ab initio} potential energy surface. Moreover, having an effective analytic model to represent such surfaces can be as important as the {\it ab initio} results themselves. For the one-dimensional potentials of diatomic molecules, the most successful such model to date is arguably the ``Morse/Long-Range'' (MLR) function developed by R.~J. Le~Roy and coworkers.\footnote{{\it Mol. Phys.} {\bf 105}, 663 (2007)
• {\it J. Chem. Phys.} {\bf 131}, 204309 (2009)
• {\it Mol.\ Phys.}\ {\bf 109}, 435 (2011).} It is very flexible, is everywhere differentiable to all orders. It incorporates correct predicted long-range behaviour, extrapolates sensibly at both large and small distances, and two of its defining parameters are always the physically meaningful well depth ${D}_e$ and equilibrium distance $r_e$. Extensions of this model, called the Multi-Dimension Morse/Long-Range (MD-MLR) function, %have been applied successfully to atom-plus-linear molecule systems\footnote{{\it Phys.\ Chem.\ Chem.\ Phys.}\ {\bf 10}, 4128 (2008)
• {\it J.\ Chem.\ Phys.}\ {\bf 130}, 144305 (2009)}, linear molecule--linear molecule systems\footnote{{\it J. Chem. Phys.} {\bf 132}, 214309 (2010).} and atom--non-linear molecule\footnote{{\it J. Chem. Phys.} {\bf 140}, 214309 (2010).} system. have been applied successfully to atom-plus-linear molecule, linear molecule--linear molecule and atom--non-linear molecule systems.\footnote{{\it Phys.\ Chem.\ Chem.\ Phys.}\ {\bf 10}, 4128 (2008)
• {\it J.\ Chem.\ Phys.}\ {\bf 130}, 144305 (2009)
• {\it J. Chem. Phys.} {\bf 132}, 214309 (2010)
• {\it J. Chem. Phys.} {\bf 140}, 214309 (2014)
• {\it J. Chem. Phys.} {\bf 144}, 014301 (2016).} However, there are several technical challenges faced in modelling the interactions of general molecule-molecule systems, such as the absence of radial minima for some relative alignments, difficulties in fitting short-range potential energies, and challenges in determining relative-orientation dependent long-range coefficients. This talk will illustrate some of these challenges and describe our ongoing work in addressing them.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

En

Permalink

http://hdl.handle.net/2142/91111

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Copyright 2016 by the authors

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