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The system calculates the energy related to Newton's Law = G * m1 * m2 / r.
Where m1 = m2 = 1/d0
Differentiating the above with respect to r, you will get Newton's Gravity Law F = G * m1 * m2 / r ^2.
Making m1 equal to m_e = 1 / d0 / lp = lp * m_e, which gives the gravitational force between two electrons.
Note since lp is very small, the simulation will take a long time.
Note only energy of p1 should be considered.