diff --git a/examples/USER/pinning/readme.md b/examples/USER/pinning/readme.md index e5563a3056..163536ca94 100644 --- a/examples/USER/pinning/readme.md +++ b/examples/USER/pinning/readme.md @@ -1,18 +1,56 @@ -This bias potential is used to study solid-liquid transitions with the interface pinning method. +This package contains a bias potential that is used to study solid-liquid transitions with the interface pinning method. +An interface between a solid and a liquid is simulated by applying a field that bias the system towards two-phase configurations. +This is done by adding a harmonic potential to the Hamiltonian. The bias field couple to an order-parameter of crystallinity Q: -Reference: + U_bias = 0.5*k*(Q-a)^2 -[Ulf R. Pedersen, J. Chem. Phys. 139, 104102 (2013)] +Here, We user long-range order for "crystallinity". Q=rho_k wher rho_k is the collective density field. -Usage snip: +# References +The main reference for the method is + [Ulf R. Pedersen, J. Chem. Phys. 139, 104102 (2013)] - fix [fix-name] [groupID] rhoKUmbrella [nx] [ny] [nz] [kappa] [anchor-point] - thermo_style custom step temp pzz pe lz f_umbrella f_umbrella[1] f_umbrella[2] f_umbrella[3] +Please visit + urp.dk/interface_pinning.htm +for a detailed bibliography. + +# Build +Remember to include the following command when building LAMMPS + make yes-user-pinning + +# Use + + fix [name] [groupID] rhok [nx] [ny] [nz] [kappa] [anchor-point] where the parameters set the harmonic bias potential U=0.5*kappa*(|rho_k|-anchor-point)^2 with the wave-vector elements of rho_k to k_x = (2 pi / L_x) * n_x, k_y = (2 pi / L_y) * n_y and k_z = (2 pi / L_z) * n_z. -This package was created by +# Usage example +In the following we will apply use the interface pinning method for the Lennard-Jones system (trunctaed at 2.5) +at temperature 0.8 and pressure 2.185. This happens to be a coexistence state-point, but we will later show how interface pinning +can be used to determine this. The present directory contains input files, that we will use. + +## Density of crystal +First we will determine the density of the crystal with the following LAMMPS input file +{crystal.lmp} +from the output we get that the average density is 0.9731. We need this density to ensure hydrostatic pressure +when in the crystal slap of a two-phase simulation. + +## Setup two-phase configuration +Next, setup a two-phase configuration using the density determined in the previous step. +{setup.lmp} + + +## Setup two-phase configuration +Finally, we run simulation with the bias field applied. +{pinning.lmp} + +# Contact Ulf R. Pedersen http://www.urp.dk ulf AT urp.dk + +# Cite +Please cite + [Ulf R. Pedersen, J. Chem. Phys. 139, 104102 (2013)] +when using the package for a publication.