Europium-doped silicon clusters EuSi n (n = 3–11) and their anions: structures, thermochemistry, electron affinities, and magnetic moments

Abstract

The structures, electron affinities, and dissociation energies of EuSi n (n = 3–11) and their anions have been examined by means of four hybrid and pure density functional theory (DFT) methods. Basis sets used in this work are of segmented (SEG) Gaussian valence basis sets and relativistic small-core effective core potentials (ECP) with additional diffuse 2pdfg functions, denoted aug-SEG/ECP for Eu atoms and aug-cc-pVTZ for Si atoms. The geometries are fully optimized with each DFT method independently. The ground-state structures for all of these species are found to be substitutional type, which can be regarded as being derived from the ground-state structure of Si n+1 (and/or Si +1 − ) by replacing a Si atom with a Eu atom. The theoretical adiabatic electron affinities (AEAs) of EuSi n predicted by the four DFT schemes are in excellent agreement with the experimental data, especially the AEAs of TPSSh and B2PLYP. The average absolute deviations from experiment are by 0.10, 0.06, 0.07, and 0.05 eV, and the largest deviations are 0.16, 0.12, 0.18, and 0.10 eV at the B3LYP, TPSSh, PBE, and B2PLYP levels, respectively. The AEA of EuSi n (n = 3–11) is less than that of Si n . With the increase in silicon cluster size, the AEA of EuSi n may be close to that of Si n , but cannot be larger than that of Si n . The Eu atom acts as an electron donor, and the bonding between Eu and silicon clusters is ionic in nature. The bond between Eu and silicon clusters of neutral EuSi n (n = 3–11) is stronger than that of the anions. The total magnetic moments of EuSi n /EuSi (n = 3–11) and the magnetic moments on the Eu atom do not quench, and the total magnetic moments are contributed by Eu atom. The dissociation energies of Eu atom from EuSi n and their anions have also been calculated to examine relative stabilities.