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

[kordzadeh at aut.ac.ir]

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

C,CR1,CH2

 

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

Regards

Azadeh

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