“…Al 4 cluster exhibits a rhomboidal structure in a triplet spin state with D 2 h symmetry, ,, in a 3 B 2g , a 3 B 3g , and a 1 A g ground state. ,, Distortion of planarity has been obtained within DFT theory using PBE0/aug-cc-pVTZ, M06-2X/aug-cc-pVTZ, and CCSD(T)/aug-cc-pVQZ . In this work we have obtained a D 2 h planar rhomboidal structure in a 3 B 3g ground state (Figure ), in agreement with previous reports. ,, The 1 A g ground state was obtained for the meta-GGA TPSS and revTPSS when the DGDZVP and DGTZVP basis sets are used and revTPSS/aug-cc-pVDZ, in agreement with previous reports ,, (Tables SI-XIII and SI-XIV) . The BL found range from 2.63 and 2.73 Å for D95 and SDecp.…”