Role of Static Displacements in Stabilizing Body Centered Cubic High Entropy Alloys

Area of Science:

• Materials Science
• Solid State Physics
• Computational Materials Science

Background:

• High entropy alloys (HEAs) are multicomponent alloys with unique properties.
• The stabilization of specific crystal structures in HEAs is often attributed to configurational entropy.
• However, the role of entropy in stabilizing the body-centered cubic (bcc) phase is debated.

Purpose of the Study:

• To investigate the role of disorder-induced atomic displacements in stabilizing the bcc phase of HEAs.
• To explore the relationship between atomic displacements and the average valence of HEAs.
• To identify non-entropic contributions to the stabilization of crystalline ground states in HEAs.

Main Methods:

• Computational modeling of HEAs to simulate atomic structures and displacements.
• Analysis of the correlation between average valence and the occurrence of the bcc structure.
• Comparison of static atomic displacements in bcc HEAs with temperature-induced vibrations in elemental metals.

Main Results:

• Configurational entropy has a minimal effect on stabilizing specific crystal structures in HEAs.
• Disorder-induced atomic displacements significantly stabilize the bcc structure in HEAs with average valences below 4.7.
• These static displacements are comparable to those associated with the Lindemann criterion for melting.

Conclusions:

• Disorder-induced atomic displacements provide a crucial mechanism for stabilizing the bcc phase in HEAs.
• A previously unrecognized non-entropic energy contribution, stemming from chemical disorder, stabilizes specific crystalline ground states in HEAs.
• The findings challenge conventional understanding and highlight the importance of static atomic disorder in HEA phase stability.