Latent Phase Transition in Two-Dimensional PdSe_{2}

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Conventional phase transitions in 2D materials involve gradual structural changes.
• Classical thermodynamics describes latent heat as energy absorption without immediate phase change.

Purpose of the Study:

• To investigate an unconventional phase transition in 2D palladium diselenide (PdSe_{2}).
• To explore mechanisms analogous to latent heat in low-dimensional materials.

Main Methods:

• In situ atomic scanning transmission electron microscopy (STEM) for real-time observation.
• Palladium atom implantation and thermal annealing.
• Density functional theory (DFT) calculations for mechanistic insights.

Main Results:

• Observed a
• latent phase transition
• in PdSe_{2} where energy is absorbed without immediate structural rearrangement.
• The 2D PdSe_{2} lattice maintained its framework until a critical internal chemical pressure triggered an abrupt collapse into a 3D Pd_{17}Se_{15} phase.
• DFT calculations confirmed the role of van der Waals gap energy buffering and weak Pd-Pd interactions in the transition.

Conclusions:

• Established a new phase transition paradigm in 2D materials, distinct from conventional gradual transformations.
• Demonstrated a phenomenon analogous to classical latent heat in a 2D material system.
• Advanced the understanding of phase engineering in low-dimensional materials.