USER-UEF is a LAMMPS package for non-equilibrium molecular dynamics (NEMD) under diagonal flow fields, including uniaxial and biaxial flow. With this package, simulations under extensional flow may be carried out for an indefinite amount of time. It is an implementation of the boundary conditions developed by Matthew Dobson, and also uses numerical lattice reduction as was proposed by Thomas Hunt. The lattice reduction algorithm is from Igor Semaev. The package is intended for simulations of homogeneous flows, and integrates the SLLOD equations of motion.

This package was created by David Nicholson (davidanich@gmail.com) at the Massachusetts Institute of Technology.

The following commands are contained in this package:

fix npt/uef and fix nvt/uef:

These commands perform time-integration of the SLLOD equations of
motion under constant temperature/pressure with the proper 
boundary conditions for extensional flow fields.

compute pressure/uef and compute temp/uef:

These commands allow for the evaluation of pressure/ke tensors in
the reference frame corresponding to the applied flow field.

dump cfg/uef:

This command dumps coordinates in the reference frame corresponding
to the applied flow field.

For more information, visit the documentation page for fix nvt/uef and examine the example scripts in doc/USER/uef/.

References:

I. Semaev, Cryptography and Lattices, 181 (2001).

M. Dobson, J. Chem. Phys., 141, 184103 (2014)

T.A. Hunt, Mol. Simul., 42, 347 (2016).

D.A. Nicholson, G.C. Rutledge, J. Chem. Phys.,145, 244903 (2016)