Thank you for your reply. We also did few more tests for the same system
with MNDO/d and AM1/d (both use d orbitals for Sulfur if we are not
mistaken). It appears that MNDO/d crashes also, but AM1/d and PM6
through Gaussian interface work well. We guess it may be related to the
way d-orbitals are handled in the PM6 sqm implementation.
Thanks,
Wei
On 09/28/2012 08:50 AM, Matthew Zwier wrote:
> We've observed this also, with systems with large spatial extents and
> containing D orbitals. Localized systems work fine, systems without D
> orbitals of any extent work fine. This is occurring in solution for
> us.
>
> MZ
>
> On Fri, Sep 28, 2012 at 10:09 AM, Gerald Monard
> <gerald.monard.univ-lorraine.fr> wrote:
>> Hi,
>>
>> I run some tests on your files. It seems indeed that only PM6 crashes at
>> some point. Other semiempirical hamiltonians do not crash (I tested AM1,
>> PM3, PM3-PDDG, and RM1). May be there is a problem in the PM6 potential
>> energy surface describing your system.
>>
>> Sincerely,
>>
>> G. Monard.
>>
>> On 09/28/2012 10:58 AM, Gerald Monard wrote:
>>> Hi,
>>>
>>> IMHO, I'm not sure that it is really a SCF convergence problem in your case.
>>> Your system is a charge separated system ( (CH3NH3^+)2 + NH4^+ (SO4H^-)2
>>> ) that you try to simulate in gas phase at T=800K. There is a really
>>> great chance that during an QM-MD, your system will blow up at some
>>> point. In a certain chemical sense, I am not sure that this is something
>>> wrong.
>>>
>>> I made some quick tests with your system (minimization before running
>>> the MD, 300K instead of 800K, vrand=10 instead of 100, etc.), but at
>>> some point there is always a proton transfer between an amine group and
>>> a sulfate, then the system explodes because of the energy released.
>>> If your system was soaked into a aqueous solvent for example, I am
>>> pretty sure that this would not happen.
>>>
>>> Sincerely,
>>>
>>> G. Monard.
>>>
>>>
>>> On 09/28/2012 01:45 AM, Wei Lin wrote:
>>>> Hi Everyone,
>>>>
>>>> I tried to run MD simulation with PM6 Hamiltonian for a small charged
>>>> cluster contained d-orbital element. After ~ 38 steps of simulation,
>>>> the system blows up with error message as follows:
>>>>
>>>> QMMM: WARNING!
>>>> QMMM: Unable to achieve self consistency to the tolerances specified
>>>> QMMM: No convergence in SCF after 1000 steps.
>>>> QMMM: Job will continue with unconverged SCF. Warning energies
>>>> QMMM: and forces for this step will not be accurate.
>>>> QMMM: E = -0.6307E+06 DeltaE = 0.1152E-01 DeltaP = 0.3365E-02
>>>> QMMM: Smallest DeltaE = 0.3550E-03 DeltaP = 0.2442E-02 Step = 787
>>>>
>>>> Then, I set up another simulation for the same system with Gaussian
>>>> interface. The simulation runs well.
>>>>
>>>> Andy Goetz suggested that can be related to SCF convergence algorithms
>>>> in sqm. I am wondering if anyone knows how to overcome this problem.
>>>>
>>>> The mdin (both in sqm and Gaussian interface), inpcrd, prmtop and run
>>>> files are attached.
>>>>
>>>> Thanks,
>>>> Wei
>>>>
>>>>
>>>> _______________________________________________
>>>> AMBER mailing list
>>>> AMBER.ambermd.org
>>>> http://lists.ambermd.org/mailman/listinfo/amber
>>
>> --
>> ____________________________________________________________________________
>>
>> Prof. Gerald MONARD
>> Theoretical Chemistry and Biochemistry Group
>> SRSMC, Université de Lorraine, CNRS
>> Boulevard des Aiguillettes B.P. 70239
>> F-54506 Vandoeuvre-les-Nancy, FRANCE
>>
>> e-mail : Gerald.Monard.univ-lorraine.fr
>> tel. : +33 (0)383.684.381
>> fax : +33 (0)383.684.371
>> web : http://www.monard.info
>>
>> ____________________________________________________________________________
>>
>>
>> _______________________________________________
>> AMBER mailing list
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>> http://lists.ambermd.org/mailman/listinfo/amber
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Received on Fri Sep 28 2012 - 10:30:02 PDT
