Comparison of FOD forces from 1509 code against Perfect code.
| FOD Forces | 15.09 | 15.09 | 15.09 | Perfect | Perfect | Perfect | |
| System | Iteration | Energy | Force | Iteration | Energy | Force | |
| O2 | 40 | -150.532208342396 | 1.93437E+00 | 40 | -150.532208340982 | 1.93437E+00 | |
| C | 35 | -37.948149980841 | 8.70048E-02 | 33 | -37.949732226438 | 5.98195E-02 | * |
| Ne | 19 | -129.280486811818 | 4.92905E-08 | 19 | -129.280486809783 | 4.93064E-08 | |
| Si | 40 | -290.009172036716 | 0.00000E+00 | 26 | -290.009493219802 | 2.72566E-03 | * |
| Ar | 22 | -528.536504273164 | 1.36560E-05 | 22 | -528.536504267612 | 1.36592E-05 | |
| Cu | 33 | -1642.9669101984 | 1.42033E-02 | 33 | -1642.96691020445 | 1.42033E-02 | |
| Zn | 19 | -1782.09202782696 | 4.29770E-01 | 19 | -1782.09202784385 | 4.29770E-01 | |
| As | 27 | -2239.09827171692 | 1.17216E-02 | 27 | -2239.09827171562 | 1.17216E-02 | |
| Kr | 30 | -2757.60622134865 | 6.05614E-03 | 30 | -2757.60622135151 | 6.05614E-03 | |
| N2 | 26 | -109.854697003805 | 1.32926E-02 | 26 | -109.854697003943 | 1.32926E-02 |
*Note that energy and convergence of C and Si are different between the two codes. It doesn't make too much sense comparing FOD forces in these two cases.