Studying the impact of diagonal-doping on thermal stability of main-group metal clusters via Born Oppenheimer molecular dynamics

Doping with a heteroatom is considered to be an effective tool in tuning the physico-chemical properties of metal clusters. Over a period of time, several experimental and theoretical investigations have been carried out to understand the effect of doping on structure, electronic properties and reactivity of main group clusters. However, issues pertaining to thermal stabilities of metal clusters, particularly in the context of heteroatom doping remain unexplored. Filling this lacuna, this report focuses on evaluating the finite temperature behaviour of the main group metal clusters which are doped with diagonally adjacent dopant atoms. Born-Oppenheimer Molecular Dynamical (BOMD) simulations are performed on diagonally doped LimMg, BemAl and BmSi (m=1−5) clusters (doped diagonal pairs). The thermal response of these doped diagonal pairs is also compared with the corresponding pristine clusters such as Lin, Mgn, Ben, Aln, Bn and Sin (n=2−6) clusters. The simulation trajectories and ionic motions are analysed and root mean square bond length fluctuations are calculated as a function of temperature. The results indicate that the diagonally doped BmSi (m=1−5) clusters are thermally more stable (1200 K) as compared to the other two doped clusters (LimMg, BemAl). The enhanced thermal stability is attributed to the higher binding energies noted for BmSi (m=1−5) clusters. Moreover, it is found that for the B-Si cluster systems, diagonal doping always enhances the thermal stability, whereas both diagonal doping and the size of the cluster affect the thermal stabilities of the LimMg, and BemAl cluster systems. An in-depth analysis of thermal-structural-electronic (frontier molecular orbitals) properties revealed that the strength of dopant-to-parent cluster interactions are playing a significant role in influencing the thermal stabilities of diagonally doped clusters. Overall this study also highlights how the heuristic chemical principle of ‘diagonal relationship’ widely used in main-group chemistry may be extended to cluster science to draw new insights regarding thermal stabilities of metal clusters.