  We study the pair description of heavy tetraquark systems $|QQ\bar Q \bar
Q\rangle$ in the frame of a non-relativistic potential model. By taking the two
heavy quark pairs $(Q\bar Q)$ as colored clusters, the four-quark Schr\"odinger
equation is reduced to a two-pair equation, when the inner motion inside the
pairs can be neglected. Taking into account all the Casimir scaling potentials
between two quarks and using the lattice QCD simulated mixing angle between the
two color-singlet states for the tetraquark system, we extracted a detailed
pair potential between the two heavy quark pairs.
