  Calculation of thermodynamic functions of the three-dimensional Ising
ferromagnet above and below critical temperature is performed in the
approximation of sixfold basis distribution ($\rho^6$ model). Comparison with
the results for the $\rho^4$ model indicates that dependence of the
thermodynamic functions on the renormalization group parameter $s$ becomes
weaker. The optimal interval of the renormalization group parameter values is
determined.
