Structure of a molecular liquid GeI4

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Germanium tetraiodide (GeI4) is a molecular liquid known to exhibit pressure-induced liquid-to-liquid phase transitions.
• Understanding the structure of the low-pressure liquid phase is crucial for characterizing its phase behavior.

Purpose of the Study:

• To establish the reference structure of the low-pressure liquid GeI4 phase.
• To investigate the temperature dependence of the liquid structure under ambient pressure.

Main Methods:

• Synchrotron X-ray diffraction measurements were performed across a range of temperatures.
• Reverse Monte Carlo (RMC) analysis was employed to model the liquid structure.
• Simulations were used to confirm findings regarding molecular size and prepeak behavior.

Main Results:

• The intramolecular Ge-I bond length (2.51 Å) is temperature-independent.
• Molecular centers exhibit self-similar distribution with heating.
• Nearest molecules show a vertex-to-face orientation inclined at ~20 degrees, leading to shorter intermolecular I-I distances.
• A prepeak in the structural factor, attributed to crystalline remnants, shifts and intensifies with temperature due to thermal expansion and reduced molecular size.

Conclusions:

• The study provides a detailed structural model for liquid GeI4.
• Thermal expansion influences molecular arrangement and the observed prepeak.
• The findings contribute to understanding the phase transitions in molecular liquids.