In 6d, V=(r_A-r_B)· (r_A-r_B)

                m_A, m_B are the masses of the two particles in electron mass units.

                Equation 2.7 of Variance Minimization becomes

                (1.1)

Ground State

     (1.2)

Where

     (1.3)

The second exponential in (1.2) makes the wave function is periodic  in x, y and z.  ..\definitions\PeriodBC  All integrals will need to be over a box of size L_xL_yL_z.

           (1.4)

                 (1.5)

Substituting into (1.1)

(1.6)

Or

                (1.7)

For kà0, and V = (r_A-r_B)² 2a²(1/m_A+1/m_A) needs to be 1 to cancel the potential.  The 1/m sum corresponds to the reduced mass.