Density functional theory for carbon dioxide crystal.

Area of Science:

• Computational Materials Science
• Physical Chemistry
• Thermodynamics

Background:

• Existing models for solid-liquid phase transitions often rely on the second-order direct correlation function.
• Describing polyatomic molecules like CO2 requires accounting for both attractive and entropic interactions.

Purpose of the Study:

• To develop a novel density functional approach for modeling the solid-liquid phase transition, interfacial and crystal structure, and properties of carbon dioxide (CO2).
• To integrate enthalpic and entropic interactions within a density functional framework.

Main Methods:

• Utilized a density functional approach based on fundamental measure theory for hard-sphere repulsion.
• Incorporated enthalpic interactions from dispersive attractions and entropic interactions from molecular architecture.
• Applied the model to predict densities and interfacial tensions of CO2.

Main Results:

• The theoretical model accurately predicts liquid and solid densities of CO2 at the equilibrium triple point, showing good agreement with experimental data.
• Predicted interfacial tensions for crystal-liquid interfaces on different planes.
• The approach offers a new method for studying phase transitions in polyatomic systems.

Conclusions:

• The developed density functional approach provides a robust framework for studying phase transitions and interfacial properties of polyatomic molecules like CO2.
• The model's predictions for CO2 densities align well with experimental observations.
• Further validation is needed to confirm the accuracy of predicted interfacial tensions.