Structure stabilization effect of vacancies and entropy in hexagonal WN
Yingna Han1, Wandong Xing2, Rong Yu3
1Department of Physics, Beijing Engineering Research Center of Detection and Application for Weak Magnetic Field, University of Science and Technology Beijing, Beijing 100083, People's Republic of China.
Summary
Hexagonal tungsten mononitride (WN) stability is enhanced by vacancies. WC-type WN with 6-8% vacancies is more stable, especially at high temperatures due to vibrational entropy.
Area of Science:
- Materials Science
- Solid State Physics
- Computational Chemistry
Background:
- Tungsten mononitride (WN) is a material with potential applications.
- Understanding the structural stability of WN is crucial for its synthesis and application.
- Previous studies proposed MnP-type and NiAs-type structures for WN.
Purpose of the Study:
- To investigate the structural stability of hexagonal tungsten mononitride (WN).
- To determine the most stable WN structure and the role of vacancies.
- To elucidate the influence of temperature and entropy on WN stability.
Main Methods:
- Combining experimental scanning transmission electron microscopy (STEM).
- Utilizing first-principles calculations (density functional theory).
- Analyzing configurational and vibrational entropy contributions.
Main Results:
- WC-type WN with 6-8 at% vacancies is found to be more stable than MnP-type and NiAs-type structures.
- Higher vibrational entropy in WC-type WN lowers the required vacancy concentration for stabilization at elevated temperatures.
- Vacancies and entropic effects significantly impact the structural stability of high-temperature synthesized compounds.
Conclusions:
- The WC-type WN structure with specific vacancy concentrations is the most stable form.
- Entropic factors, particularly vibrational entropy, play a critical role in stabilizing WN at high temperatures.
- This study highlights the importance of considering vacancies and entropy in designing and synthesizing stable inorganic compounds.
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