  The problem of improving the reliability of perturbative QCD predictions at
moderate energies is considered. These predictions suffer from substantial
renormalization scheme dependence, which is illustrated using as an example the
QCD effective charge appearing in the static interquark potential and the QCD
corrections to the Gross-Llewellyn-Smith sum rule in the deep inelastic
neutrino-nucleon scattering. To reduce this scheme dependence, it is proposed
to use a modified perturbation expansion, based on a modified couplant, which
is perturbatively consistent with the conventional running coupling parameter,
but is free from Landau singularity and has smaller renormalization scheme
dependence. The modified couplant is obtained by integrating the
renormalization group equation with an appropriately constructed nonpolynomial
generator. The renormalization scheme dependence of the perturbative
predictions in the modified expansion is discussed in detail, including the
predictions selected by the Principle of Minimal Sensitivity. It is shown that
the modified predictions are much more stable with respect to change of the
renormalization scheme parameters than the predictions obtained in the
conventional approach. It is also found that the modified predictions display
somewhat weaker energy dependence than the predictions obtained with the
conventional expansion, which may be interesting from the point of view of
comparing the low energy and high energy determinations of the strong coupling
parameter.
