Crystal-amorphous and crystal-crystal phase transformations via virtual melting.

Area of Science:

• Materials Science
• Thermodynamics
• Condensed Matter Physics

Background:

• Phase transformations (PTs) between crystalline (c) and amorphous (a) states are crucial in materials science.
• Internal stresses play a significant role in driving and mediating these phase transformations.
• Existing models do not fully capture the complex interplay between stress, atomic mobility, and phase transitions.

Purpose of the Study:

• To introduce and thermodynamically/kinetically justify a novel mechanism of virtual melting (VM) for phase transformations and stress relaxation.
• To develop new scenarios for crystal-amorphous and crystal-crystal phase transformations by combining VM with nonequilibrium PT diagrams.
• To reinterpret phase transformation mechanisms in materials, using ice Ih as a case study.

Main Methods:

• Thermodynamic and kinetic justification of the virtual melting (VM) mechanism.
• Integration of VM with nonequilibrium phase transformation (PT) diagrams.
• Application of the developed model to analyze phase transformation mechanisms in ice Ih.

Main Results:

• Virtual melting (VM) was identified as a mechanism for internal stress relaxation and phase transformations.
• VM reduces interface friction, lowers kinetic barriers, and enhances atomic mobility.
• The VM mechanism can decrease the thermodynamic melting temperature of materials.
• New scenarios for crystal-amorphous and crystal-crystal PTs were developed by combining VM with nonequilibrium PT diagrams.

Conclusions:

• The virtual melting (VM) mechanism provides a unified framework for understanding crystal-amorphous and crystal-crystal phase transformations and stress relaxation.
• This mechanism offers a new interpretation of phase transformation processes in ice Ih.
• The findings are broadly applicable to various materials exhibiting stress-induced phase transitions.