[DFTB-Plus-User] DFTB-Plus-User Digest, " vary the number of valence electrons per atom"

Xiaobao xiaobaojsyz at 163.com
Tue Mar 26 15:41:28 CET 2013 

Thank you. I will try those options.

Best,
xiaobao


At 2013-03-26 19:00:02,dftb-plus-user-request at dftb-plus.info wrote:
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>Today's Topics:
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>   1. Re: vary the number of valence electrons per atom (Jan M. Knaup)
>   2. Re: vary the number of valence electrons per atom (B?lint Aradi)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Mon, 25 Mar 2013 17:22:26 +0100
>From: "Jan M. Knaup" <Jan.Knaup at bccms.uni-bremen.de>
>To: "User list for DFTB+ related questions"
>	<dftb-plus-user at dftb-plus.info>
>Subject: Re: [DFTB-Plus-User] vary the number of valence electrons per
>	atom
>Message-ID:
>	<CAEz4Yq1un+vd-W1a6fRUd-UTP_u1J82OwLUXpDd-swFw29oLJQ at mail.gmail.com>
>Content-Type: text/plain; charset="iso-8859-1"
>
>Dear xiobao,
>
>I do not fully understand what you intend to do but I assume, you want to
>add a certain ammount of electrons to a number of atoms you specify.
>This cannot be done directly, and you cannot ensure that the electrons stay
>where you put them in the first place.
>First of all, the point charges are in the ElectricField section of the
>input, which indicates that they are part of the external potential. These
>point charges are not electrons in the system, they only interact through
>the electrons as an external potential in the SCC cycle.
>If you want to change the total charge of the system, you need to do so by
>setting the Charge Keyword in the Hamiltonian section, i.e.:
>
>Hamiltonian=DFTB{
>...
>Charge=1.23456
>...
>}
>
>You can tell DFTB+ to put this charge on certain atoms at the beginning of
>the SCC iteration be setting the InitialCharges option. Please refer to the
>manual for details of this option as it offers several possibilities.
>At any rate, this will only set the initial charge upon starting the first
>SCC iteration of your simulation. The final charge distribution will be the
>result of the self-consistent charge solution.
>
>So, if I understood your intentions right, you have to calculate the change
>in total charge by yourself, by adding all the charge variations you want
>to apply, then specify these variations as InitialCharges. However, this
>will not enforce an atomic charge variation, it will only suggest it at the
>beginning of the SCC cycle.
>
>Best,
>Jan
>
>Jan M. Knaup                      | Fon +49-(0)421-218-62351
>Dipl. Phys. Dr. rer. nat.         | Fax +49-(0)421-218-62770
>Universit?t Bremen - BCCMS        |
>Am Fallturm 1                     | Jan.Knaup at bccms.uni-bremen.de
>28359 Bremen                      | JanKnaup at gmail.com
>Germany                           | www.bccms.uni-bremen.de
>
>
>2013/3/24 Xiaobao <xiaobaojsyz at 163.com>
>
>>  Hi,
>> Would anyone know how to vary the number of valence electrons per atom
>> using code? I have tried to put extra point charge on each atom in my
>> system, but seems likes the net charge of the system did not change at all.
>> I would appreciate if you can give some idea about this issue. My code for
>> this part is:
>>  ElectricField={
>>   PointCharges={
>>   CoordsAndCharges [Angstrom] = {
>> 3.537814    4.984055    78.185036    0.02
>> 3.539401    4.982467    74.324043    0.02
>> 2.76839    3.899242    76.254594    0.02
>> 2.76839    3.899242    80.115486    0.02
>> 3.515588    1.669818    76.254609    0.02
>> 0.417256    3.869608  &nbsp ; 76.254501    0.02
>> 3.515588    1.669818    80.115525    0.02
>> 0.417256    3.869608    80.115625    0.02
>> }
>> }
>> }
>> Thanks in advance!
>>
>> xiaobao
>>
>>
>>
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>------------------------------
>
>Message: 2
>Date: Tue, 26 Mar 2013 08:52:52 +0100
>From: B?lint Aradi <balint.aradi at bccms.uni-bremen.de>
>To: User list for DFTB+ related questions
>	<dftb-plus-user at dftb-plus.info>
>Subject: Re: [DFTB-Plus-User] vary the number of valence electrons per
>	atom
>Message-ID: <515153D4.3090409 at bccms.uni-bremen.de>
>Content-Type: text/plain; charset="utf-8"
>
>Hi Xiaobao,
>
>If you want to simulate a sort of doping in your system by changing the
>number of valence electrons of the constituting atoms (also called the
>virtual crystal approach), you can change the number of electrons in the
>second line of the homo-nuclear Slater-Koster files. Description of the
>SK-files can be found at
>
>http://www.dftb.org/parameters/introduction/
>
>  Best regards,
>
>  B?lint
>
>
>-- 
>Dr. B?lint Aradi
>Bremen Center for Computational Materials Science, University of Bremen
>http://www.bccms.uni-bremen.de/cms/people/b_aradi/
>
>
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