[gmx-users] difference between force constants in various force field

kordzadeh at aut.ac.ir kordzadeh at aut.ac.ir
Tue Jan 16 16:24:37 CET 2018

Hi every one

I have a question

I want to obtain topology of carbon nano tube with x2top but I must determine the value of bond strength and angle constant.

I think we have a bond carbon-carbon that stretches with a constant force for example in amber force field this constant is 392459  kj /(mol nm^2) for interaction CA-CA but in gromos force field this constant is define differently....

I don't know what should I do

I 'm confused, in gromos

define gb_17   0.14    8.5400E+6



8.54 e 6 is force constant for stretch bond and dimention is kj/(mol nm^2), am I right?

then we can conclude that if I want to determine force constant , I must select these constant wwith respect to force field , 

I can't say these constants are same every where.rigth?

is the dimention of constant kj/(mol nm^2) every where in gromacs, such as .itp files of force field, itp files that we receive form ATB and so on?

any suggestion will be appreciated

Thank you very much



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