二.The non-ideal gas 3 2 1 0 -2 repulsive attractive 3 1.5 2.0 2.5 3.0 3.5 4.0 distance The Lennard-Jones energy versus distance 二 Xi’an University of Science & Technology . The non-ideal gas The Lennard-Jones energy versus distance -3 -2 -1 0 1 2 3 4 1.5 2.0 2.5 3.0 3.5 4.0 distance Energy repulsive attractive