Thanks David. I have the same problem with ntt=3.
I quickly tried with small natural dipeptides Ala-Phe:
CH3O-Ala-Phe-COOH, CH3O-Ala-Phe-COOMe, CH3O-Ala-Phe-COO and I had the
same issue during the SA only for the CH3O-Ala-Phe-COOH as expected.
Best regards,
Baptiste
Le 07/11/2012 15:46, David A Case a écrit :
> On Wed, Nov 07, 2012, Baptiste Legrand wrote:
>
>> During the
>> calculations on a specific compound, the temperature is not controled
>> and "vlimit exceeded" errors occured during the SA protocol and the
>> system blow up for some structures:
>>
>> NSTEP = 1800 TIME(PS) = 10.900 TEMP(K) = 735.86 PRESS
>> NSTEP = 2000 TIME(PS) = 11.000 TEMP(K) = 10363.98 PRESS
>> NSTEP = 2200 TIME(PS) = 11.100 TEMP(K) = 7826.16 PRESS
> You need to have enough temperature control to prevent getting temperatures of
> 10,000 degrees. I'd recommend trying ntt=3 for this. Note that there is no
> real equivalent of tautp then: you have to just change the target temperature
> as a function of time to get the temperature profile you want.
>
> (ntt=3 offers better temperature regulation, especially for smallish systems,
> or systems without explicit solvent. Note that it is quite common to have to
> experiment a bit with a simulated annealing input to get a temperature vs.
> time profile that is effective.)
>
> You may also have a problem with the COOH group, but try the above first.
>
> ...good luck...dac
>
>
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Received on Thu Nov 08 2012 - 01:30:03 PST
