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Collective acoustic modes in liquids: a comparison between the generalized-hydrodynamics and memory-function
F Aliotta1, J Gapiński, M Pochylski
1CNR-IPCF, Laboratorio di Tecniche Spettroscopiche, Messina, Italy. aliotta@me.cnr.it
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 21, 2011
Summary
Generalized hydrodynamics and memory function models for liquid dynamics are not equivalent. Memory function models can inaccurately represent spectral profiles due to misinterpretations, especially near relaxation processes.
Area of Science:
- Condensed matter physics
- Theoretical physics
- Chemical physics
Background:
- Dynamical structure factor in liquids is crucial for understanding material properties.
- Generalized hydrodynamics and memory function approaches are common theoretical frameworks.
- Previous studies often assume equivalence between these two methods.
Purpose of the Study:
- To investigate the equivalence of generalized hydrodynamics and memory function approaches.
- To identify limitations of memory function models in describing liquid dynamics.
- To clarify the theoretical basis for discrepancies in spectral profile predictions.
Main Methods:
- Theoretical analysis of dynamical structure factor models.
- Comparison of spectral profiles predicted by generalized hydrodynamics and memory function approaches.
- Examination of memory function expressions and their interpretation.
Main Results:
- The generalized hydrodynamics and memory function approaches are not fully equivalent.
- Memory function models, particularly those using normalized damped oscillators, fail for systems near relaxation.
- Misinterpretation of memory function expressions leads to mixing of spectral contributions across different wave vectors.
Conclusions:
- The common belief in the full equivalence of these methods is challenged.
- Careful interpretation of memory function theory is essential to avoid inaccuracies.
- The findings necessitate a re-evaluation of theoretical models for liquid dynamics, especially under specific conditions.
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