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LAMMPS : The Irreversible mechanical deformation – Viscosity

Viewed : 175 times,  2021-10-26 01:59:33

Plastic deformation occurs when external stress is applied to the material that exceeds its elastic limit. In the case of amorphous materials, plastic deformation occurs in a similar way to the flow of liquids. Therefore, this can be explained by the viscous flow mechanism.

In particular, the quantity of viscosity (η) is a fundamental factor in determining such viscous flow. Viscosity is a time-dependent characteristic.

For more Information on this topic, please refer to the “ Viscoelastic properties of polymers" article.


This module tip aims to find the viscosity of a certain polymer system as a function of temperature using the LAMMPS (Viscosity) module.



Calculation Procedure

We need the successfully finished ‘LAMMPS (Thermalization)’ module to calculate the viscosity .

You can perform the thermalization calculation by referring to the following posts.

  1. Modeling: How to perform the polymer simulation – Polymer MD Modeling
  2. Structure optimization (Thermalization): The Essential Step for Polymer Simulation – Thermalization


The calculation is conducted via the Green-Kubo method, an equilibrium molecular dynamics calculation. Therefore, we cannot adjust the strain rate. The average viscosity of the material can therefore be calculated in this way.



Calculation Results



👉 View the example work


Following the calculation, you can check the resulting viscosity data as a function of temperature and time, as shown in the example above.



Example Video




🍀  Need more Information?

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