Neutron diffuse scattering in deuterated para-terphenyl, C(18)D(14).

Area of Science:

• Materials Science
• Condensed Matter Physics
• Crystallography

Background:

• Short-range order (SRO) describes local atomic or molecular arrangements in materials.
• Deuterated para-terphenyl exhibits complex molecular dynamics influencing its crystalline structure.

Purpose of the Study:

• To investigate the nature and extent of short-range order in deuterated para-terphenyl using neutron diffuse scattering.
• To understand the correlations between molecular twists and their impact on crystal structure.

Main Methods:

• Neutron diffuse scattering experiments were conducted at various temperatures.
• Monte Carlo simulations were employed to model the observed correlation structures and molecular dynamics.

Main Results:

• Incipient Bragg peaks at 200 K indicate negative correlations in central phenyl group twists along a and b directions.
• Correlation range is approximately three times longer along the b-direction than the a-direction.
• Molecular displacements are strongly positively correlated in the ab-plane, especially along a, while weaker along c.

Conclusions:

• The study elucidates the anisotropic short-range order in deuterated para-terphenyl, driven by molecular twists.
• The interplay between molecular twist occupancies and displacive motions explains the observed correlation patterns.
• These findings contribute to understanding molecular interactions and order in crystalline systems.