Knowledge Bank

Extensive calculations have been undertaken on the ground state of $H3\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$, with is Gaussian functions as basis functions. No ``atomic-like'' functions were used, and the function positions as well as exponents were treated as variable parameters. Careful energy minimization was done on an IBM 7072 computer by the pattern search technique. For the $D2b$ geometry ($\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A11$ electronic state) electron correlation has been accounted for by the use of configurations having different orbitals for different spins. Approximate Hartree-Fock molecular orbital functions have also been obtained. The many-configuration functions are energetically better than those of a recent configuration interaction $study1$ which used Slater type orbitals (STO's) as basis functions. For example, at $R=1.6575$ bohrs a 7 configuration Gaussian function gives $E=-1.33410$ hartrees as compared to $E=-1.33264$ hartrees for the best 12 configuration STO wavefunction. Further calculations are in progress, and will be reported. A critical comparison will be made of the Gaussian results with those of the STO wavefunctions, and with the 26 term correlated wavefunctions of $Conroy.2$ Comments will be offered on the equilibrium internuclear distance, the convergence to the exact energy, and the correlation energy.