Impurity effects on solid-solid transitions in atomic clusters.

Area of Science:

• Computational materials science
• Condensed matter physics
• Nanotechnology

Background:

• Low-temperature anomalies in vibrational heat capacity (C_V) of nanoclusters are linked to competing solid-like phases.
• Solid-solid transition temperatures (T_s) are defined by the crossover of free energies between these phases.

Purpose of the Study:

• To investigate the effect of single atom substitution on low-temperature anomalies in nanocluster vibrational heat capacity.
• To explore the tunability of solid-solid transitions and heat capacity peaks by impurity modification.

Main Methods:

• Harmonic superposition approach applied to model nanoclusters.
• Utilized Lennard-Jones potentials for selected clusters.
• Employed the many-body Gupta potential for Ni₇₄X and Au₅₄X clusters (X = Au, Ag, Al, Cu, Ni, Pd, Pt, Pb).

Main Results:

• Single atom substitution can tune the solid-solid transition temperature (T_s) and C_V peak by altering impurity size and binding strength.
• Excessive atom-size mismatch can disrupt existing transitions and induce new ones.
• Observed up to two additional C_V peaks below T_s, indicating impurity delocalization within the ground-state geometry.

Conclusions:

• Finite-system analogues of solid-solid transitions in nanoalloys can be tuned, engineered, and suppressed through controlled atom substitution.
• Impurity effects offer a pathway to manipulate the vibrational and phase behavior of nanoclusters.