The importance of an accurate target wave function in variational calculations for (e^{+}-H_{2}) scattering

TL;DR

This paper demonstrates that the accuracy of the target wave function critically affects variational calculations of positron scattering on H2, showing that more sophisticated wave functions yield more reliable phase shifts and annihilation parameters.

Contribution

The study introduces a systematic approach to assess and improve the reliability of variational scattering calculations by optimizing the target wave function accuracy.

Findings

Results are highly sensitive to wave function accuracy.

More sophisticated wave functions improve calculation reliability.

Discrepancies between theory and experiment are discussed.

Abstract

Using the complex Kohn method, we have calculated variational values of phase shifts and the annihilation parameter, Z_{eff}, for the elastic scattering of positrons by molecular hydrogen. Our results are sensitive to small changes in the accuracy of the wave function representing the target hydrogen molecule. We have developed a systematic approach to demonstrate that, at low positron energies, there are particular forms of the Kohn trial wave function for which the results of variational calculations are not reliable, even when the target wave function accounts for as much as 96.8% of the correlation energy of H_{2}. We find that reliable results can be recovered if our calculations are extended to admit more sophisticated target wave functions accounting for 99.7% of the correlation energy. Remaining discrepancies between theory and experiment are briefly discussed.