Knowledge Bank

The recent observation by Sharpe, Zeng, Wittig, and Beaudet of a highly bent geometry for the HBr--$CO2$ van der Waals molecule was quite surprising in light of the linear configurations for both HF--$CO2$ and HCI--$CO2$. To investigate the origin of these different structures we have calculated potential functions for the three HX-$CO2$ complexes. The model (previously applied to (HCCH)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$, HCCH--$CO2$, and ($CO2$)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$) contains dispersion, repulsion, and electrostatic interactions which are distributed among the atoms of the monomer molecules. The potential functions for the three HX--$CO2$ species, which were constructed without any freely adjustable parameters are in good agreement with experimental observations. The resulting equilibrium geometrics will be discussed in terms of the relative competition between repulsive and attractive terms in the potential function.