# The impact of electron correlations on the energetics and stability of silicon nanoclusters

The first-principles prediction of stable nanocluster structure is often hampered by the existence of many isomer configurations with energies close to the ground state. This fact attaches additional importance to many-electron effects beyond density functional theory (DFT), because their contributions can change a subtle energy order of competitive structures. To analyze this problem, we consider, as an example, the energetics of silicon nanoclusters passivated by hydrogen Si10H2n (0< n <11), where passivation changes the structure from compact to loosely packed and branched. Our calculations performed with DFT, hybrid functionals and Hartree-Fock (HF) methods, as well as by the GW approximation (GWA), confirm a considerable sensitivity of isomer energy ordering to many-electron effects.