Theoretical Study of the Spin Competition in Small-Sized Al Clusters

Abstract

Stern-Gerlach (SG) experiments on aluminum clusters indicate that some small-sized aggregates exhibit a deflection signal consistent with the existence of magnetic moments. However, in the particular case of Al6 and Al8 clusters, electronic structure investigations show ambiguity on the 0 K ground spin state. In this work extensive computations of the electronic structure have been carried out in order to determine the ground state of these structures. Electron correlation has been introduced at MP2, MP4, and CCSD(T) theory level as well as by DFT computations with different density functionals. DFT-based Born-Oppenheimer molecular dynamics results at different simulation temperatures complete this investigation. One of our main conclusions is that singlet spin states are systematically the more stable configuration at 0 K. These Al clusters exhibit almost degenerate electronic structures at singlet and triplet spin states. The geometries are similar, and the paths connecting both structures allow an intersystem crossing through a spin-orbit coupling mechanism, indicating a dynamical interchange of both spin states at finite temperatures.

A Global Optimizer for Nanoclusters

“…We have built the global minimum structures of Al nanoclusters up to Al 12 with PyAR|XTB, and up to Al 8 with PyAR|BP86. There are several theoretical studies on Al clusters at various levels of theory, such as Sutton-Chen empirical potential (Joswig and Springborg, 2003), DFT (Ahlrichs and Elliott, 1999; Rao and Jena, 1999), and CCSD(T) (Shinde and Shukla, 2014; López-Estrada and Orgaz, 2015).…”

Reassessment of the Four-Point Approach to the Electron-Transfer Marcus–Hush Theory

“…Al 2 has been observed to have two local minima both experimentally 91 and theoretically. 92 The spectroscopy experiment reports a 3 ∏ u electronic ground state with a bond length of 2.7011 ± 0.0015 Å and a vibrational frequency of 285.80 cm –1 . Similarly, a 3 ∑ g – electronic state with a bond length of 2.4665 ± 0.0024 Å and a vibrational frequency of 350.01 cm –1 has been reported.…”

“…85,90 In such an attempt, we discuss the error of employing the distinct averages in a model system of an aluminum dimer, which has been extensively investigated both experimentally 91 and theoretically. 92 This simple model, while not an ET system, allows us to explore analytically the reorganization energies as well as the driving force by noting that the Marcus−Hush theory can be seen as a method to find the intersection between the parabolas along the reaction coordinate. The analysis of the relative error allows us to explore novel donor and acceptor molecules used in organic photovoltaics by means of the averaged reorganization energy.…”

Magnetic and vibrational properties of small chromium clusters on the Cu(111) surface

“…14 The structure, and electronic and magnetic properties of small free and supported Cr and other transition metal magnetic clusters have been extensively investigated experimentally [15][16][17][18][19] and theoretically. [20][21][22][23][24][25] There has been found a strong interplay between the atomic structure and magnetic order in the clusters. Thus, for Cu(111) surface supported small clusters of Fe, Mn, and Cr it has been revealed that the Fe clusters show ferromagnetic order regardless of the cluster geometry.…”