Structure stabilization effect of configuration entropy in cubic WN.

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Materials Science

Background:

• Understanding the structural stability of transition metal nitrides like tungsten nitride (WN) is crucial for their application in extreme conditions.
• High-pressure, high-temperature synthesis methods often result in complex phases and defect structures.
• The role of entropy and external stimuli, such as electron irradiation, in phase stability requires detailed investigation.

Purpose of the Study:

• To elucidate the microscopic structure and phase stability of cubic tungsten nitride (WN).
• To investigate the influence of temperature and electron beam irradiation on the structural transitions in WN.
• To provide insights into the synthesis and stability of materials under high-pressure, high-temperature conditions.

Main Methods:

• Combined experimental and computational approach using scanning transmission electron microscopy (STEM).
• First-principles calculations based on density functional theory (DFT) were employed.
• Analysis of electron beam irradiation effects on the WN structure.

Main Results:

• NaCl-type cubic WN with disordered vacancies is more stable at high temperatures due to configurational entropy.
• Electron beam irradiation was observed to induce an order-disorder phase transition in cubic WN.
• Ordered NbO-type WN can potentially be obtained through annealing below the transition temperature.

Conclusions:

• Configurational entropy plays a significant role in stabilizing disordered phases of WN at elevated temperatures.
• Electron beam irradiation offers a pathway to control the ordering of vacancies in cubic WN.
• The findings contribute to understanding the stability and synthesis of materials produced under extreme conditions.