Knowledge Bank

On the basis of the assignment of infrared spectra in a solid argon matrix, Sommer, et $al.1$, and Weltner and $Warn2$ proposed the $C2v$ V-structure for the $B2O3$ molecule. However, the interbond angle $\phi$ could not be determined from such considerations, and values of $\phi$ of 120 $degrees2$ and of 95 to 150 $degrees1$ seemed compatible with the assignment of the infrared spectra. In order to find the value of $\phi$ by theoretical methods, a series of all valence electron SCF MO calculations in the INDO approximation were made, assuming bondlengths as suggested by Weltner and Warn and with interbond angle $\phi$ varying from 90 to 180 degrees. An energy minimum is found to occur for $\phi =102$ degress. Since the accuracy of the assumed bondlengths is uncertain, results of similar calculations with different bondlengths and the value of $\phi$ at which minimum energy occurs will be reported to show the sensitivity of the value of $\phi$ to the assumed bondlengths. Results for the relative energetic stability of the $C2v$ V-structure, as compared to alternative structures proposed, will also be presented. Results of maximum overlap method calculations will be presented in order to provide a rationale for understanding physically the results of INDO calculations.