[gmx-users] angle constraints

[tarak karmakar]

Oh ! Thnaks
I saw that table, the angle_restrain option is there but not constraints .
Anyway if suppose, I fix the distance between the two terminal atoms
of the molecule, the angle will eventually be fixed at a particular
given value. Is that the logic ?
Actually I searched for this problem so many times but didn't get
proper clue; in one of those mails I saw someone has dealt with some
dummy atoms. I could not able to digest that logic.

On Tue, Jul 24, 2012 at 11:01 AM, Mark Abraham <Mark.Abraham at anu.edu.au> wrote:
> On 24/07/2012 3:21 PM, tarak karmakar wrote:
>>
>> Dear All,
>>
>>
>> I am constraining one angle in my protein sample by incorporating " [
>> constraints ]" block in topology file as
>>
>>
>> [ constraints ]
>> ;  index1  index2  index3   funct     angle
>>   6064 6063 6065     1   180.0
>>
>> while doing that its showing the following error
>>
>> Program grompp, VERSION 4.5.5
>> Source code file: topdirs.c, line: 174
>>
>> Fatal error:
>> Invalid constraints type 6065
>> For more information and tips for troubleshooting, please check the
>> GROMACS
>> website at http://www.gromacs.org/Documentation/Errors
>
>
> As you will see in table 5.6, this is not a valid option for [constraints] -
> you can only specify bonds. You will need to construct a triangle of bond
> constraints.
>
> Mark
>
>
>>
>>
>> Then I rechecked the angle block, that specific angle is there in that
>> angle section, part of it as follows
>>   6039  6057  6058     1
>>   6039  6057  6059     1
>>   6058  6057  6059     1
>>   6064  6063  6065     1
>>   6067  6066  6068     1
>>   6067  6066  6069     1
>>   6068  6066  6069     1
>>   6071  6070  6072     1
>>   6071  6070  6073     1
>>   6072  6070  6073     1
>>
>> [ constraints ]
>> ;  index1  index2  index3   funct     angle
>>   6064 6063 6065     1   180.0
>>
>> [ dihedrals ]
>> ;  ai    aj    ak    al funct            c0            c1
>> c2            c3            c4
>>
>>
>
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-- 
Tarak