Dear Maxim:
I'm so sorry to disturb you again,but I've completed the kpoint grid
convergence with a reletive high value of Meshcutoff just follow your
words.Then I've got many FORCE_STRESS files related to different kpoint
grid.In these files the first four lines is just as follows：
-1470.4169519132
-0.000001407 -0.000000013 0.000000004
-0.000000013 0.000000460 0.000000004
0.000000004 0.000000004 0.000050126
I want to know what does the first line "-1470.4169519132" mean?And you've
told me the parameter used to convergence test is Force.Is Force you mean
the value " -1470.4169519132" or the next 3*3 matrix
-0.000001407 -0.000000013 0.000000004
-0.000000013 0.000000460 0.000000004
0.000000004 0.000000004 0.000050126
?
Thans very very much .
Dexi Shao
2014-07-25 20:39 GMT+08:00 邵德喜 <dxshao...@gmail.com>:
> Thanks very very much for all your replay,saluted all of you !
> Dexi Shao
>
>
> 2014-07-25 19:22 GMT+08:00 Максим Арсентьев <ars21031...@gmail.com>:
>
> Yes, you right.
>> To clarify 1st keep fixed high meshcutoff and vary kpoint -> select
>> kpoint and keep it fixed but vary meshcutoff
>> Maybe this can be vice versa, or not,but possibly it is not so important
>> (final value of meshcutoff about 350-400 Ry, sometimes for late heavy
>> transition metal elements, with oxygen maybe it can be more)
>>
>>
>> 2014-07-25 5:53 GMT+04:00 邵德喜 <dxshao...@gmail.com>:
>>
>> I see.You mean that I should set CG steps as usual as we do structual
>>> relaxation(foer example :500) during all the convergence tests .
>>> And consider kpoint grid convergence first with a reletive high value
>>> of Meshcutoff.When it is done ,plot how it depends on FORCES from
>>> the output file in the final convergency step .Then consider meshcutoff
>>> convergence test with the convergency kpoint grid.
>>> When the convergence tests is completed ,structual relaxation is also
>>> completed,so I do not need to do structual relaxation additionally.
>>> Is it all right?
>>> Thanks for all your replay!
>>> ( PS: I‘m so sorry but the service is just out of work.I'll upload my
>>> input fdf file as soon as it recovers.)
>>> Dexi Shao
>>>
>>>
>>> 2014-07-25 1:14 GMT+08:00 Максим Арсентьев <ars21031...@gmail.com>:
>>>
>>> Dear Dexi!
>>>>
>>>> You should not set nember of CG steps to zero - it is not necessary.
>>>> You right that you should perform convergence of your property of interest,
>>>> but first structural relaxation is important as I suppose - maybe not in
>>>> your case, but often it is so. So select high meshcutoff about 400-500 and
>>>> vary density of kpoint grid and plot how it depends on FORCES. From this
>>>> plot you will select kpoints, then take this kpoints fixed and vary
>>>> meshcutoff to plot dependence on forces again. It is forces, not total
>>>> energy are relevant for structural relaxation. Enter in google "graphene
>>>> transiesta" and 1st link will help I believe.
>>>>
>>>> четверг, 24 июля 2014 г. пользователь 邵德喜 написал:
>>>>
>>>> Thanks very much.The unit is Ry.
>>>>> I was told that when I get the original structure ,I should do
>>>>> convergence tests first,structual relaxation comes second.
>>>>> In my opinion ,do convergence test without structual relaxation I
>>>>> should set CG step to zero.
>>>>> problem1:I check the convergency (in terms of gradually increase
>>>>> Meshcutoff) of the total energy may be useless
>>>>> because I was told "we should check the convergence not of the total
>>>>> energy but of those properties which are relevant for our study in
>>>>> question
>>>>> ".
>>>>> But I just want to study the current-voltage relation ,it's expensive
>>>>> for me to check the convergence of its transport property.
>>>>> So I check the convergence of total energy instead opportunisticly.
>>>>> The input.fdf file is as follows.
>>>>> Thans for your replay.
>>>>> Dexi Shao
>>>>>
>>>>>
>>>>> 2014-07-24 18:22 GMT+08:00 Kanhao Xue <xuekan...@gmail.com>:
>>>>>
>>>>>> Dear Dexi,
>>>>>>
>>>>>> I wonder what is the unit of your Mesh cutoff? Is it in Ry?
>>>>>>
>>>>>> Siesta is using atomic orbital as the basis, which is quite different
>>>>>> from plane-wave based codes like VASP. In plane-wave code, the plane wave
>>>>>> cutoff energy directly determines your basis, and thus influences the
>>>>>> result a lot.
>>>>>>
>>>>>> In Siesta we have the mesh cutoff concept. A large cutoff is required
>>>>>> for accurate result. Usually for LDA, 250 Ry is sufficient and for GGA
>>>>>> 350
>>>>>> Ry is sufficient.
>>>>>>
>>>>>> In my opinion you do not need to go up to 600 Ry to check.
>>>>>>
>>>>>> However, indeed your energy changes too much with Mesh cutoff. Can
>>>>>> you upload your input fdf file for more information?
>>>>>>
>>>>>> Kanhao
>>>>>>
>>>>>>
>>>>>> On Thu, Jul 24, 2014 at 11:43 AM, 邵德喜 <dxshao...@gmail.com> wrote:
>>>>>>
>>>>>>> Dear everyone:
>>>>>>> I have done the convergence test when I check the convergency (in
>>>>>>> terms of gradually increase Meshcutoff) of the total energy, I found
>>>>>>> that
>>>>>>> the Total energy rise up when I increase the parameter of Meshcutoff
>>>>>>> (please refer to the accesory) .Is it reasonable?
>>>>>>> Ahy replay will be appreciated.
>>>>>>> Dexi Shao
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>>
>>>>>> Sincerely yours,
>>>>>> Kanhao Xue
>>>>>>
>>>>>> Laboratoire de Réactivité et Chimie des Solides (LRCS)
>>>>>> UMR CNRS 7314
>>>>>> Université de Picardie Jules Verne
>>>>>> 33 Rue Saint Leu, 80039 Amiens Cedex, France
>>>>>>
>>>>>
>>>>>
>>>>
>>>> --
>>>> Best wishes,
>>>> Maxim Arsent'ev, D.Sc.(Chemistry)
>>>> Laboratory of research of nanostructures
>>>> Institute of Silicate Chemistry of RAS
>>>>
>>>>
>>>
>>
>>
>> --
>> Best wishes,
>> Maxim Arsent'ev, D.Sc.(Chemistry)
>> Laboratory of research of nanostructures
>> Institute of Silicate Chemistry of RAS
>>
>
>
