Which Is the Lowest-Energy Structure of Al13 Clusters: Assessment of Different Exchange-Correlation Functionals in Density Functional Theory

Several low-energy isomers of neutral Al-13 cluster were revealed via empirical genetic algorithm and further optimized by ab initio calculations. In addition to the well-known icosahedron for Al-13 with l(h) symmetry, a non-symmetric C-1 configuration was found to be energetically competitive, and their energy sequence depends on the choice of the exchange-correlation functionals. HF method or functionals incorporating with LYP correlation parameterization (BLYP, B3LYP, X3LYP) prefer the C-1 isomer, while the l(h) isomer was recognized as the lowest-energy structure by those functionals with Perdew's correlation parameterization, such as PW91, PBE, PBEO, B3PW91. In contrast, the choice of basis set has little influence on the energy sequence of these two Al-13 isomers. The present results imply that the theoretical lowest-energy structure of an atomic cluster may depend sensitively on the choice of functional.