Low-lying Ptn cluster structures (n=6-10) from global optimizations based on DFT potential energy surfaces: Sensitivity of the chemical ordering with the functional

Through the example of the small Pt-6 clusters the low-lying structures and their chemical ordering obtained with the four classes of functionals: GGA (PBE), hybrid GGA (PBE0), meta-GGA (TPSS) and-hybrid meta-GGA (TPSSh), were investigated with the cc-pVTZpp basis set. Moreover, the spin multiplicities from singlet to nonet were considered. The results yield two different pictures: singlet to septet planar structures are favored with the pure functionals while quintet to nonet 3D structures appear as the lowest energy structures or first isomers for their hybrid counterpart. Qualitative trends obtained from ROMP4(SDQ) calculations suggest a more correct description at the DFT level by the use of hybrid functionals. The investigation of the lowest energy structures of Pt7-10 clusters at the TPSSh level in comparison with the GGA picture issuing from the literature confirm the preference for 3D compact structures. This highlights a different morphological map of the small Pt-n clusters and suggests a clearer pattern growth from Pt-6 toward the lowest energy Pt-10 structure. (C) 2017 Elsevier B.V. All rights reserved.