deltap[deltaT_,deltav_]:=4 deltaT - 6 deltaT deltav - 3/2 deltav^3 ;

Plot3D[deltap[deltaT,deltav],{deltaT,-7,7},{deltav,-7,7},ColorFunction->"DarkRainbow",AxesLabel->Automatic,PlotRange->{-300,300}]

Export["vanderWaals.jpg",]