Bulk viscosity in the case of the interatomic potential depending on density

Area of Science:

• Condensed Matter Physics
• Thermodynamics
• Materials Science

Background:

• Existing bulk viscosity (zeta) formulas rely on macroscopic quantities like pressure.
• A microscopic understanding of zeta, particularly in density-dependent systems, is lacking.
• Previous work established a zeta formula for density-independent potential systems.

Purpose of the Study:

• To derive a generalized formula for bulk viscosity (zeta) in density-dependent potential systems.
• To establish a direct relationship between microscopic quantities (interatomic potentials, pair distribution functions) and macroscopic zeta.
• To provide a new theoretical framework for analyzing bulk viscosity in variable-density systems.

Main Methods:

• Derivation of a generalized bulk viscosity (zeta) formula.
• Expression of zeta using microscopic parameters: interatomic potentials and pair distribution functions.
• Application of the derived formula to a model liquid metal with density-varying interatomic potentials.

Main Results:

• The new formula successfully relates microscopic properties to the macroscopic bulk viscosity (zeta).
• Calculations for a model liquid metal show zeta increases where interatomic potentials transition with density.
• The derived theoretical relationship offers a new perspective on bulk viscosity.

Conclusions:

• The developed formula provides a valuable tool for understanding bulk viscosity in complex systems.
• The findings offer a microscopic interpretation of bulk viscosity changes in response to density variations.
• Qualitative agreement with experimental data for liquid mercury supports the formula's validity.