Small magnesium clusters: between van der waals and valence bonds

Area of Science:

• Condensed Matter Physics
• Quantum Chemistry
• Materials Science

Background:

• Small metal clusters are of fundamental interest in understanding the transition from atomic to bulk properties.
• Previous experimental data on small magnesium clusters are scarce, limiting theoretical validation.

Purpose of the Study:

• To experimentally characterize magnesium molecules Mg(2), Mg(3), Mg(4), and Mg(5) for the first time.
• To determine the structures and vibrational frequencies of these clusters.
• To compare experimental results with theoretical predictions from density functional theory.

Main Methods:

• Isolation of magnesium molecules (Mg(2)-Mg(5)) in rare-gas matrices at cryogenic temperatures (8 K).
• Characterization using Raman spectroscopy to identify vibrational frequencies.
• Comparison of experimental data with density functional theory (DFT) calculations.

Main Results:

• Experimental observation and characterization of Mg(2), Mg(3), Mg(4), and Mg(5) clusters.
• Determination of the fundamental frequency for Mg(2) at 97 cm⁻¹ in an Argon matrix.
• Calculated bond lengths: Mg(2) (340.8 pm), Mg(3) (317.8 pm), Mg(4) (301.3 pm), and Mg(5) (293.1, 322.5 pm).
• Predicted structures: Mg(3) (triangular, D3h), Mg(4) (tetrahedral, Td), Mg(5) (trigonal-bipyramidal, D3h).

Conclusions:

• The study provides the first experimental evidence and characterization of small magnesium clusters.
• The results validate theoretical predictions for the structures and vibrational properties of these clusters.
• The tetramagnesium cluster is identified as a matrix-isolated magic number cluster, significant for cluster science.