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Experimental triplet and quadruplet fluctuation densities and spatial distribution function integrals for liquid
Elizabeth A Ploetz1, Paul E Smith1
1Department of Chemistry, Kansas State University, 213 CBC Building, Manhattan, Kansas 66506, USA.
The Journal of Chemical Physics
|March 10, 2015
Summary
This study extends Kirkwood-Buff theory to calculate higher-order molecular fluctuations and integrals in liquid mixtures using only thermodynamic data, revealing composition-dependent correlations.
Area of Science:
- Physical Chemistry
- Thermodynamics
- Statistical Mechanics
Background:
- Kirkwood-Buff (KB) theory traditionally analyzes pair fluctuations and integrals from thermodynamic data.
- Extending KB theory to higher-order fluctuations (triplet, quadruplet) is crucial for a deeper understanding of liquid mixtures.
- Existing methods often rely on structural data, limiting thermodynamic approaches.
Purpose of the Study:
- To develop a purely thermodynamic method for determining triplet and quadruplet fluctuations and integrals.
- To apply this method to binary mixtures like water + methanol and benzene + methanol.
- To investigate the influence of composition on molecular correlations and fluctuations.
Main Methods:
- Utilized Kirkwood-Buff or Fluctuation Solution Theory principles.
- Calculated triplet and quadruplet fluctuations and integrals from experimental thermodynamic data.
- Avoided the use of structure factors in the analysis.
Main Results:
- Successfully derived triplet and quadruplet fluctuations and integrals using only thermodynamic data.
- Observed significant variations in species correlations with composition in water + methanol and benzene + methanol mixtures.
- Found that the magnitude of fluctuations and integrals increases with the polarity of the involved molecules.
Conclusions:
- The developed thermodynamic approach effectively provides higher-order molecular fluctuations and integrals.
- Composition and molecular polarity significantly impact correlation behavior in binary liquid mixtures.
- The findings offer a simplified physical model to explain observed fluctuation variations.
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