  We obtain a travelling-wave solution of a generalised nonlinear Schr\"odinger
equation with an additional term of the form $\Gamma(\psi(x,t)) = \lambda
\psi(x,t)^q$, where $\lambda$ and $q$ are real constants. Moreover, we show
that the density of energy of the system for the travelling-wave solution
presents a Lorentzian solitary wave behaviour.
