TABLE II: Comparison of − ϵ HOMO energies (in a.u.) for some molecules calculated using BLYP, FT97 and PBE XC functionals, with literature data. BLYP and experimental results are taken from refs. [26] and [44] respectively. See text for details. Molecule − ϵ HOMO Molecule − ϵ HOMO BLYP FT97 PBE Expt. BLYP FT97 PBE Expt. Na 2 0.1002 0.0862 0.0952 0.1798 NaH 0.1421 0.1231 0.1324 — Mg 2 0.1530 0.1293 0.1395 — AlH 0.1715 0.1362 0.1521 — MgH 2 0.2221 0.1857 0.2024 — SiH 0.1597 0.1305 0.1514 0.2900 AlH 2 0.1631 0.1253 0.1468 — Al 2 0.1400 0.1161 0.1318 0.1984 PH 0.2133 0.1786 0.2012 0.3730 SiH 2 0.2027 0.1619 0.1808 0.3278 SH 0.2174 0.1809 0.1994 0.3830 HSe 0.2057 0.1746 0.1903 0.3618 PH 2 0.2111 0.1741 0.1970 0.3610 SiH 3 0.1969 0.1590 0.1825 0.2990 HBr 0.2603 0.2249 0.2439 0.4292 HI 0.2432 0.2122 0.2302 0.3817 PH 3 0.2287 0.1854 0.2054 0.3627 H 2 S 0.2190 0.1815 0.2006 0.3843 H 2 Se 0.2075 0.1731 0.1916 0.3635 SiH 4 0.3156 0.2702 0.2919 0.4042 P 2 0.2526 0.2206 0.2360 0.3870 S 2 0.2023 0.1594 0.1781 0.3438 Se 2 0.1951 0.1576 0.1749 0.3160 Br 2 0.2451 0.2115 0.2285 0.3865 H 2 S 2 0.2288 0.1928 0.2103 0.3418 S 3 0.2294 0.1985 0.2143 — P 4 0.2575 0.2369 0.2525 0.3432 — — — — — for a set of 6 atoms using this approach to assess its level of performance and effective- ness in the said domain. For all these, we use LDA XC potential, STO-3G basis set and N$_{r}$ = 128 , h$_{r}$ = 0 . 3. We are not aware of any other attempts where such studies have been made within the LCAO framework, using CCG only. Besides the point mentioned above in this paragraph, there are other important motivations for this case study, which have been elaborated in Section I. These are all open-shell systems and a thorough comparison with the GAMESS program is made for all of them, using same basis set as well as same XC functional. Following quantities are reported: kinetic energy 〈 T 〉 , nuclear-electron attrac- tion energy 〈 V$_{ne}$ 〉 , classical Hartree energy 〈 E$_{h}$ 〉 , exchange energy 〈 E$_{x}$ 〉 , correlation energy 〈 E$_{c}$ 〉 , two-electron potential energy 〈 V$_{ee}$ 〉 , total potential energy 〈 V 〉 , total electronic energy 〈 E 〉 , total integrated electron density N as well as all the α - and β -spin orbital energies. Note that literature results employ Euler-McLaurin and Gauss-Legendre quadratures for radial and angular integrations respectively. The default grid option is used for all these reference results. Individual Coulomb repulsion and XC energies from literature could not be cited as GAMESS output does not report those. Quite clearly, for all these quantities, agreement with literature results is excellent (very similar accuracy, as we observed in the 10