van der Waals Equation (p+a/Vi)(V-b)=nRT V'msel =V'm-b repulsion Pog =p+alv attraction Xi’an University of Science & Technology van der Waals Equation ( )( ) 2 , 2 / / m m m eff m eff m p a V V b nRT V V b p p a V + − = = − = + repulsion attraction