[Smeagol-discuss] End of File reached
Zheng Xiaohong
exhzheng at gmail.com
Thu Mar 26 00:35:56 GMT 2009
Hello, Ivan,
It is very clear now. Thank you very much.
Xiaohong
Ivan Rungger wrote:
> Hello,
>
> I think there is a bit of misunderstanding. The following applies for
> systems that are periodic in the x-y plane, for wires always use 1
> k-point only. There is no constraint in the code that forces the number
> of k-points in the leads calculation to be equal to the one of the
> scattering region. So in principle you can use any value, however in the
> following I write what I suggest to do:
>
> A smeagol calculation for the extended molecule (EM) and periodic
> systems consists of two parts:
> 1) the convergence of the charge density matrix (DM):
> for this part one should always use the same number of x-y k-points in
> leads and scattering region, because that will help convergence. If the
> x-y k-points are different an artificial scattering is created at the
> place where the leads are joined to the EM, which leads to convergence
> problems. So although it is not strictly necessary, it is better to
> always use the same number of x-y kpoints as in the leads.
> 2) the calculation of the transmission coefficient and current for the
> converged DM:
> Usually step 1) is the difficult/time consuming one, while 2) is much
> faster. Moreover it is often the case (e.g. in magnetic tunnel
> junctions) that the DM can be converged with few xy kpoints (e.g. 7x7 or
> 10x10), but that the transmission can only be calculated correctly if
> many kpoints are used (e.g. 100x100). Therefore one can use a kgrid of
> few kpoints for step 1), and then setup a separate calculation for the
> TRC, where a much finer k-grid is used (using the converged DM and
> setting Maxscfiterations 1, so that no self-consistency is performed).
> In this case there is no problem if the number of kpoints does not match
> the leads.
>
> Hope this helps,
>
> Ivan
>
>
>
>
> Xiaohong Zheng wrote:
>
>> Hello, Sagar and Ivan,
>>
>> Since calculations with different k meshes in the lead and scattering
>> region go on very well, perhaps the block in the scattering region like
>>
>> %block kgrid_Monkhorst_Pack
>> 4 0 0 0.0
>> 0 4 0 0.0
>> 0 0 1 0.0
>> %endblock kgrid_Monkhorst_Pack
>>
>> is just for the transmission, not for the density matrix. The k mesh
>> for the density matrix will be obtained from the lead calculation
>> automatically? If this is the case, then we do not have to give the same
>> k point number along x and y directions in the lead and transport file
>> for the kgrid block. I do not know. Please Ivan give us the correct answer.
>>
>> Xiaohong
>>
>>
>> ambavale sagar wrote:
>>
>>
>>> Dear Xiaohong,
>>> You are correct. There is no constraint that your k-point mesh for
>>> transport calculation in scattering file and k-point mesh for density
>>> matrix calculation in the same scattering file must be same.
>>> But I could not see the any special parameter for defining different
>>> k-point mesh for density matrix and transport calculation in the same
>>> scattering file.
>>> On the other way it is necessary to have k-pt mesh in x-y direction
>>> same in leads file and for density matrix calculation in scattering
>>> file. So I answered like that..
>>>
>>> Hope Ivan will correct me If there is something wrong in my
>>> understanding..
>>>
>>>
>>> Regards
>>> Sagar Ambavale
>>>
>>> --- On *Thu, 19/3/09, Xiaohong Zheng /<exhzheng at gmail.com>/* wrote:
>>>
>>>
>>> From: Xiaohong Zheng <exhzheng at gmail.com>
>>> Subject: Re: [Smeagol-discuss] Smeagol-discuss Digest, Vol 15, Issue 9
>>> To: "ambavale sagar" <sagarambavale at yahoo.co.in>
>>> Cc: smeagol-discuss at lists.tchpc.tcd.ie
>>> Date: Thursday, 19 March, 2009, 6:40 PM
>>>
>>> Hello, Sagar,
>>>
>>> I have a different idea about setting up the k points for the lead
>>> and transport calculations. Several days ago, I tried to set
>>> different k points for the lead and transport along x and y
>>> directions, the calculations went on very well. Then how to
>>> understand this if it is a requirement for the numbers of k points
>>> along x and y directions to be the same in both lead and transport
>>> calculations?
>>>
>>> From the discussions of ATK manual, the transport calculation will
>>> use the same k mesh as the lead for the density matrix, but a
>>> different k mesh for transmission can be specified. Can we or how
>>> can we set a different k mesh for the transmission calculations in
>>> Smeagol? Shall the k mesh for both the density matrix and the
>>> transmission be exactly the same?
>>>
>>> Best,
>>> Xiaohong
>>>
>>>
>>> ambavale sagar wrote:
>>> > Dear Serhan,
>>> > Yes, number of k-points in z-direction must be 1. While no. of k
>>> pts in x and y direction may have any values though they should be
>>> same in both lead and transport calculations.
>>> >
>>> > if you may have k-points for leads
>>> > 4 0 0
>>> > 0 4 0
>>> > 0 0 100
>>> >
>>> > then transport file must have
>>> > 4 0 0
>>> > 0 4 0
>>> > 0 0 1
>>> >
>>> >
>>> > Regards
>>> > Sagar Ambavale
>>> >
>>> >
>>> >
>>> > Message: 1
>>> > Date: Wed, 18 Mar 2009 06:15:24 +0200
>>> > From: Serhan Yamacli <syamacli at gmail.com
>>> </mc/compose?to=syamacli at gmail.com>
>>> > </mc/compose?to=syamacli at gmail.com
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>>> >
>>> > Hi asa,
>>> >
>>> > Thank you very much for the answer. Must I use the k points as
>>> >
>>> > 1 0 0
>>> > 0 1 0
>>> > 0 0 1
>>> >
>>> > always during transport calculation? But I can take such as
>>> >
>>> > 1 0 0
>>> > 0 1 0
>>> > 0 0 100
>>> >
>>> > during leads calculation? Thanks again.
>>> >
>>> > Cheers
>>> > Serhan
>>> >
>>> > 2009/3/18 asa aravindh <mails2asa at gmail.com
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