Dear all users
I want to calculate the melting point for tip4p.
- I have used this paper(paper is attached) for comparing the results.there is a big difference between total energies.
The order of energies of mine is 1000 Kcal/mol, but theirs is 10 Kj/mol.(I have attached my results and my input file) . when I use the thermo_modify norm yes,The order of energy is more logical, but it is not correct yet(file is attached).
- I have used npt ensemble and p=1 (unit real) and constant temperature. It is been seen that the pressure fluctuates widely.(pressure file is attached ). I have used pchain and tchain and drag commands for solving the fluctuation, but it did not work.
Could you help me with these problem,please?
etotal.txt (916 Bytes)
2-The melting point of ice Ih from.pdf (1.32 MB)
etotal with thermo modify.txt (204 Bytes)
input.in (2.43 KB)
peressure (847 Bytes)
Dear all users
I want to calculate the melting point for tip4p.
- I have used this paper(paper is attached) for comparing the results.there is a big difference between total energies.
The order of energies of mine is 1000 Kcal/mol, but theirs is 10 Kj/mol.(I have attached my results and my input file) . when I use the thermo_modify norm yes,The order of energy is more logical, but it is not correct yet(file is attached).
- I have used npt ensemble and p=1 (unit real) and constant temperature. It is been seen that the pressure fluctuates widely.(pressure file is attached ). I have used pchain and tchain and drag commands for solving the fluctuation, but it did not work.
Could you help me with these problem,please?
etotal.txt (916 Bytes)
2-The melting point of ice Ih from.pdf (1.32 MB)
etotal with thermo modify.txt (204 Bytes)
input.in (2.43 KB)
peressure (847 Bytes)
this questions has already been answered, but in addition i would like to remark, that the description of the methodology in that paper is very detailed and lucid and it should be very easy to reproduce those simulations with LAMMPS, but it requires some care, attention to detail, and requires proper preparatory work and equlibration. whether this has been done cannot be told from a single input file and some numbers. also the property that you were looking for, is never computed but only inferred from the total energy behavior.
overall, the advice remains the same: you need to talk to somebody that can supervise that you are doing proper system setup and equilibration and has experience with simulations. this is not a case of just sticking a few magic parameters into the input and it suddenly will work.
as for the pressure fluctuations, i’d also like to remark that you should not use the drag parameter for this kind of simulations, since you are after sensitive properties. drag does modify the dynamics and you will no longer be in the NPT ensemble. the better approach would be to set up a larger system and do proper setup and pre-equilibration.
axel.