Hi Alan,<br><br>So is acpype using a conversion factor of 4.184 for dihedral force constant?<br><br>I found some dihedral constants as 0.156 in the amber format, which should be 0.156*4.184=0.652704 in gromacs unit. However, acpype gave a force constant of 0.65084 after conversion, which is slightly off. I wonder if this is OK, and I suspect it might be that I used rdparm to check the amber format value, which only gives 3 decimals for force constants.<br>
<br>Thanks for the reply,<br>Yun<br><br><br>>Hi Yun,<br>
><br>
>ACPYPE is working fine. What happens here is I choose the >reproduce the<br>
>exact values one sees in AMBER.<br>
><br>
>Now why GMX tip3p file choose a different value, I don't know.<br>
><br>
>Nevertheless, it's pretty simple to put whatever value you want there >if you<br>
>think you need.<br>
><br>
>Alan