Tetrahedral clustering in molten lithium under pressure

Area of Science:

• Condensed matter physics
• Materials science
• Computational chemistry

Background:

• Understanding the behavior of alkali metals under extreme conditions is crucial for materials science.
• Previous studies on lithium under pressure have indicated complex phase transitions.

Purpose of the Study:

• To investigate the electronic and structural properties of molten lithium at high pressures and temperatures.
• To identify novel phases and transitions in lithium under extreme conditions.

Main Methods:

• First-principles calculations were employed to simulate molten lithium.
• Electronic structure and local ordering were analyzed at pressures above 150 GPa and temperatures up to 1000 K.

Main Results:

• A new phase of lithium was predicted, exhibiting tetrahedral local order and reduced electrical conductivity.
• Weakly bound tetrahedral clusters were observed, despite the absence of covalent bonding.
• Evidence for anomalous melting behavior above 20 GPa, with a decreasing melting temperature, was found.
• The stabilization mechanism involves electron localization and core electron interactions.

Conclusions:

• Molten lithium exhibits complex electronic and structural transitions under high pressure.
• A novel, potentially sp3-bonded-like phase with unique electronic properties exists in pressurized lithium.
• The findings suggest the possibility of new low-symmetry crystalline phases in lithium.