Structural, Energetic, Electronic, and Vibrational Properties of Boron-Substituted Tungsten Clusters

Abstract

We report a study of the density functional theory of the structural, electronic and vibrational properties of small tungsten-boron clusters using the B3LYP exchange-correlation functional together with the QZVP basis set. A large number of possible isomeric structures were generated using the USPEX code interfaced with Gaussian 03, and the lowest-energy configurations were selected for detailed analysis. The results show that the addition of boron significantly modifies the geometry of tungsten clusters by reducing their symmetry and leading to the formation of shorter and stronger W-B and B-B bonds. With increasing boron concentration, boron atoms preferentially occupy edge and outer positions and gradually form interconnected B-B links within the clusters. These structural modifications improve the overall stability of the clusters, as reflected by the increase in binding energy, HOMO-LUMO energy gap, ionization potential, and chemical hardness with increasing boron concentration. The eigenvalue spectra show a greater separation between the occupied and unoccupied electronic states after boron substitution, indicating enhanced electronic stabilization and stronger electron localization. Vibrational analysis further reveals a gradual shift from low-frequency W-W vibrational modes in pure tungsten clusters to higher-frequency W-B and B-B stretching modes in boron-rich clusters, indicating an increase in the covalent character of bonding. Overall, the results show that boron improves the stability of tungsten clusters by modifying their bonding and electronic properties at the atomic scale