27th Nov, 2016
University of Limerick
Question
Asked 25th Nov, 2016
Is the morse potential cutoff (rc) we give is the local cutoff ? Is this potential require other cutoff a global cutoff?
I am using Morse potential to address the interactions between the pair of atoms. The cutoff usually I see in papers is very small (~5 angstrom). The typical potential from used in simulations is
E = De.((1-exp(-a(r-r0)))**2 - 1.0)
The problem that I am facing is that when I am using a cutoff less than r0 (equilibrium distance) I am getting the correct structure parameters and there is no issue. If I increase the cutoff more than r0 I am not getting correct results. If anyone used this Morse potential before please help me .
All Answers (3)
What you mean by structure parameters??RDF? Whats the system you are working on??how did you measure the structure parameters? Fix the cut-off to 12 Angstroms.
I am using GULP program to calculate the bulk modulus, elastic constants and equilibrium lattice constant. The material is SnTe it is a solid thermoelectric material. I am using different cutoff for different pair of atoms for example, 5 angs fro Sn-Sn interactions and 4 angs for Sn-Te interactions and so on. The Morse potential form is shown below
E = De.((1-exp(-a(r-r0)))**2 - 1.0)
We are fitting the potential parameters for this SnTe material using DFT data. During fitting I am getting r0 > rcut for Sn-Sn pair. This potential is able to reproduce the all above mentioned experimental values with <2% error. But my doubt is that is it correct using r0>rcut?
Similar questions and discussions
How to work with SiC particles in Al matrix using LAMMPS? All pair coeffs are not set, why I’m getting this error?
# ------------ Variables definition -----------------------------------------
variable a equal 4.04527 # Al lattice parameter - FCC
variable b equal 4.3484 # SiC lattice parameter - diamond cubic material
variable c equal $a+$b
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variable e equal $a*10
variable f equal $b*10
#-------------- Crystal Structure definition ------------------------------
region whole block 0 $d 0 $d 0 $d units box
create_box 3 whole
lattice fcc $a orient x 1 0 0 orient y 0 1 0 orient z 0 0 1 spacing 1 1 1 origin 0 0 0
region box block 0 $e 0 $e 0 $e units box
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lattice diamond $b orient x 1 0 0 orient y 0 1 0 orient z 0 0 1 spacing 1 1 1
region box2 block $e $d $e $d $e $d units box
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#------------ Defining the interaction between potentials ----------------
pair_style hybrid/overlay eam/fs tersoff
pair_style eam/fs
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#------------ Relaxing the structure -------------------------------------------------------
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# ---------------- Error after running the program ----------------------
ERROR: All pair coeffs are not set (../pair.cpp:236)
Last command: minimize 1e-25 1e-25 10000 10000
All pair coeffs are not set ---- why I am getting this error???
LAMMPS tutorial on fracture of graphene
This GitHub repository (https://github.com/nuwan-d/fracture_of_grahene) contains a MATLAB script to generate the LAMMPS input files for the molecular dynamics simulation shown below. Additional MATLAB scripts are available to post-process the simulation outputs.
This tutorial can be helpful to graduate students who are relatively new to MD simulations.
Good luck!
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