TY - JOUR TI - Theoretical Analysis of the Effects of Hydrogenation in Hydrocarbons: Accurate SCF MO Wavefunctions for C2H2, C2H4, and C2H6 AU - Buenker, Robert J. AU - Peyerimhoff, Sigrid D. AU - Whitten, Jerry L. T2 - The Journal of Chemical Physics AB - A close relationship between the hydrocarbon molecule series acetylene to ethane and the homonuclear diatomic molecules N2 to F2 is demonstrated by means of accurate SCF calculations for each of these systems and C2. This fact enables one to analyze changes in corresponding orbital energies between members of the hydrocarbon series and C2 concisely in terms of three well-defined effects: changes in CC bond lengths, selective participation of hydrogen AO's in the hydrocarbon MO's, and a nonbonded interaction due to electron withdrawal from hydrogen atoms. This analysis, in turn, makes it possible to explain changes in minimum ionization potential in the hydrocarbon series and the relationship between bond lengths and binding energies between members of both series. DA - 1967/3/15/ PY - 1967/3/15/ DO - 10.1063/1.1840998 VL - 46 IS - 6 SP - 2029-2039 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.1840998 DB - Crossref ER - TY - JOUR TI - Study of Linear Stretch in Polyatomic Molecules: Accurate SCF MO Wavefunctions for CO2 and BeF2 AU - Peyerimhoff, Sigrid D. AU - Buenker, Robert J. AU - Whitten, Jerry L. T2 - The Journal of Chemical Physics AB - Accurate SCF MO calculations are carried out for CO2, BeF2, and various AH2 and AH3 molecules as a function of internuclear distance. It is noted that the resulting sum of orbital-energy curves show minima at much smaller internuclear distances than the corresponding total energy curves, even though it has previously been shown that derivatives of ET and ∑ εi with respect to internuclear angle quite generally vanish at approximately equal angles. This distinction emphasizes the point that the close correlation between angular derivatives of ET and ∑ εi is in large part caused by the lack of changes in internuclear distances between closely interacting atoms in the process of angular variations. It is further shown that an elementary application of Koopman's theorem enables one to make qualitative determinations of both relative bond angles and relative bond lengths by adding or subtracting various differentiating orbital-energy curves to an appropriate total-energy curve. DA - 1967/3// PY - 1967/3// DO - 10.1063/1.1840925 VL - 46 IS - 5 SP - 1707-1716 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.1840925 DB - Crossref ER -