  Theory of massless scalar field $\phi$ with interaction $g \phi^3$ in
six-dimensional space is considered. A possibility of initial scale invariance
breaking, which results in a spontaneous arising of effective interaction $G
\phi^4$, is studied by application of Bogolubov quasi-averages approach. It is
shown, that compensation equation for form-factor of this interaction in
approximation up to the third order in $G$ has a non-trivial solution. The
conditions imposed on form-factor value at zero and scalar field mass $m$ fix
the unique solution, which gives relations between parameters of interaction $g
\phi^3$ and parameters $G $ and $m$. Arguments are laid down in favour of a
stability of the non-trivial solution.
