A new generic model potential for mesogenic systems: square well line potential of variable range.

Area of Science:

• Computational physics and chemistry
• Soft matter physics
• Statistical mechanics

Background:

• Traditional molecular potentials like Gay-Berne and Kihara often involve numerous adjustable parameters.
• Simulating complex molecular interactions, especially for long chain molecules, presents computational challenges.

Purpose of the Study:

• To develop a simplified, analytical pair potential for approximating linear n-site square well interactions.
• To introduce the Square Well Line (SWL) potential, offering physical meaningfulness and fewer parameters.

Main Methods:

• Derivation of the analytical Square Well Line (SWL) potential.
• Utilizing Monte Carlo (MC) simulations to test the SWL potential against existing models.
• Applying Onsager-like theories to investigate phase transitions.

Main Results:

• The SWL potential accurately reproduces distance and orientation dependence of multisite pair energy.
• The SWL potential shows good agreement with MC simulations for vapor-liquid binodal of square well dumbbells.
• The SWL potential's interaction range parameter (s(2)) influences nematic-smectic A transitions similarly to ionic strength in real systems.

Conclusions:

• The SWL potential provides a computationally efficient and physically meaningful alternative for simulating molecular systems.
• The SWL model is suitable for simulating long chain molecules and for use in perturbation theory.
• The SWL potential offers new insights into the factors governing phase transitions in soft matter systems.