Insight into Point Defects and Complex Defects in β-Mo₂C and Carbide Evolution from First Principles.

Area of Science:

• Materials Science
• Computational Materials Science
• Solid State Physics

Background:

• Understanding point defects and their combinations is crucial for tailoring material properties.
• Molybdenum carbide (Mo₂C) is a significant material with potential applications influenced by its defect structures.
• First principles calculations offer a powerful tool for investigating complex defect phenomena in materials.

Purpose of the Study:

• To investigate point defects, Vanadium-related defects, and defect combinations in molybdenum β-Mo₂C using first principles methods.
• To explore the utility of first principles calculation data in analyzing the relationships between different carbides and the impact of doping elements.
• To establish the main characteristics of structural and electronic property changes during defect optimization.

Main Methods:

• Utilized first principles calculations to model and optimize supercell models with various defect types.
• Calculated formation energies for different intrinsic and combined defect complexes.
• Analyzed structure evolution and electronic properties during optimization.

Main Results:

• Carbon vacancy (V_C) is stable but not always present in pure β-Mo₂C.
• Interstitial site II is highly unstable; atoms tend to move to interstitial site I.
• Substitution of Mo with V (S_V-Mo) is the most stable single point defect.
• Complexes of multiple S_V-Mo defects are more stable than other defect combinations.
• Increasing S_V-Mo in the (Mo, V)₂C system influences material properties.

Conclusions:

• First principles data is valuable for understanding defect behavior and V-doping effects in Mo₂C.
• The study highlights the stability of S_V-Mo defects and their complexes.
• The findings provide insights into the evolution of V- and Mo-rich carbides and their potential applications.