[lammps-users] would you please answer to the 2 questions in LAMMPS?

Dear Friends

Would you please answer to the following questions?

1.I read in the manual the K coefficient of harmonic angle_coeff usually equal to 1/2
in the manual has been written:
"Note that the usual 1/2 factor is included in K"
but one of the examples of this section is:
angle_style harmonic
angle_coeff 1 300.0 107.0

therefore in the example K value equal to 300. Why is the difference (1/2 and 300).

2.what is the K value of a water molecule?

Thanks alot for your time and attention.

Best Regards

Nahid

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Nahid:

(1) Please look at a reference such as the book by Allen and Tildesley for more details about this. What the text is saying is that the harmonic angle energy is normally written as (1/2) * K; in LAMMPS, you just specify (1/2 * K) instead of K.

(2) There is no “right” answer for this–especially since there are about 100 different models for water! Some models, using SHAKE for example, even exclude that term altogether.

–AEI