viscosity.out

This file contains the stress auto-correlation function and the running viscosity from the Green-Kubo method. It is produced when invoking the compute_viscosity keyword in the run.in input file.

File format

This file reads

  • column 1: correlation time (in units of ps)

  • column 2: \(\langle S_{xx}(0)S_{xx}(t)\rangle\) (in units of eV\(^2\))

  • column 3: \(\langle S_{yy}(0)S_{yy}(t)\rangle\) (in units of eV\(^2\))

  • column 4: \(\langle S_{zz}(0)S_{zz}(t)\rangle\) (in units of eV\(^2\))

  • column 5: \(\langle S_{xy}(0)S_{xy}(t)\rangle\) (in units of eV\(^2\))

  • column 6: \(\langle S_{xz}(0)S_{xz}(t)\rangle\) (in units of eV\(^2\))

  • column 7: \(\langle S_{yz}(0)S_{yz}(t)\rangle\) (in units of eV\(^2\))

  • column 8: \(\langle S_{yx}(0)S_{yx}(t)\rangle\) (in units of eV\(^2\))

  • column 9: \(\langle S_{zx}(0)S_{zx}(t)\rangle\) (in units of eV\(^2\))

  • column 10: \(\langle S_{zy}(0)S_{zy}(t)\rangle\) (in units of eV\(^2\))

  • column 11: \(\eta_{xx} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{xx}(0)S_{xx}(t')\rangle dt'\) (in units of Pa s)

  • column 12: \(\eta_{yy} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{yy}(0)S_{yy}(t')\rangle dt'\) (in units of Pa s)

  • column 13: \(\eta_{zz} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{zz}(0)S_{zz}(t')\rangle dt'\) (in units of Pa s)

  • column 14: \(\eta_{xy} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{xy}(0)S_{xy}(t')\rangle dt'\) (in units of Pa s)

  • column 15: \(\eta_{xz} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{xz}(0)S_{xz}(t')\rangle dt'\) (in units of Pa s)

  • column 16: \(\eta_{yz} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{yz}(0)S_{yz}(t')\rangle dt'\) (in units of Pa s)

  • column 17: \(\eta_{yx} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{yx}(0)S_{yx}(t')\rangle dt'\) (in units of Pa s)

  • column 18: \(\eta_{zx} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{zx}(0)S_{zx}(t')\rangle dt'\) (in units of Pa s)

  • column 19: \(\eta_{zy} = \frac{1}{k_{\rm B}TV}\int_0^t\langle S_{zy}(0)S_{zy}(t')\rangle dt'\) (in units of Pa s)

Note:

  • The shear viscosity can be calculated as \(\eta_{\rm S} = \frac{1}{3} \left( \eta_{xy} + \eta_{xz} + \eta_{yz} \right)\).

  • The longitudinal viscosity can be calculated as \(\eta_{\rm L} = \frac{1}{3} \left( \eta_{xx} + \eta_{yy} + \eta_{zz} \right)\).

  • The bulk viscosity \(\eta_{\rm B}\) can be calculated from \(\eta_{\rm B} + \frac{4}{3} \eta_{\rm S} = \eta_{\rm L}\).

  • We have the following symmetric property, \(\eta_{\alpha\beta} = \eta_{\beta\alpha}\), which should be confirmed by the output data.