  The non-additive non-interacting kinetic energy is calculated exactly for
fragments of H$_2$, Li$_2$, Be$_2$, C$_2$, N$_2$, F$_2$, and Na$_2$ within
partition density-functional theory. The resulting fragments are uniquely
determined and their sum reproduces the Kohn-Sham molecular density of the
corresponding XC functional. We compare the use of fractional orbital
occupation to the usual PDFT ensemble method for treating the fragment energies
and densities. We also compare Thomas-Fermi and von Weiz{\"a}cker approximate
kinetic energy functionals to the numerically exact solution and find
significant regions where the von Weiz{\"a}cker solution is nearly exact.

Chemical Physics