[Pw_forum] Re: Pw_forum digest, Vol 1 #1031 - 1 msg

[Reinout Declerck]

Hi,

> If you fix the magnetization with "nelup/neldw" or with
> "multiplicity" or with "tot_magnetization", you should
> not specify starting_magnetization

if you did specify the starting_magnetization, will it affect the results?

Regards,

Reinout Declerck

----- Original Message ----- 
From: "Paolo Giannozzi" <giannozz at nest.sns.it>
To: <pw_forum at pwscf.org>
Sent: Friday, June 16, 2006 9:50 AM
Subject: Re: [Pw_forum] Re: Pw_forum digest, Vol 1 #1031 - 1 msg


> On Friday 16 June 2006 08:22, aarti srirangarajan wrote:
>
>> Also I could not find any info on how to fix the spin moments
>> in INPUT_PW  file.
>
> this is the documentation of the relevant variables (for LSDA),
> slightly modified wrt the official version (admittedly not a marvel
> of clarity).
> -------------------------------------------------------------------------------
> starting_magnetization(i)
>               REAL
>               starting spin polarization (values between -1 and 1)
>               on atomic type 'i' in a spin-polarized calculation.
>               Breaks the symmetry and provides a starting point for
>               self-consistency. The default value is zero, BUT a value
>               MUST be specified for AT LEAST one atomic type in spin
>               polarized calculations. Note that if start from zero
>               initial magnetization, you will get zero final magnetization
>               in any case. If you desire to start from an 
> antiferromagnetic
>               state, you may need to define two different atomic species
>               corresponding to sublattices of the same atomic type.
>               If you fix the magnetization with "nelup/neldw" or with
>               "multiplicity" or with "tot_magnetization", you should
>               not specify starting_magnetization
> nelup, neldw   REAL
>               number of spin-up and spin-down electrons, respectively
>               Note that this fixes the final value of the magnetization.
>               The sum must yield nelec that must also be specified
>               explicitly in this case. Not valid for spin-unpolarized
>               or noncollinear calculations, only for LSDA. Obsolescent:
>               use multiplicity or tot_magnetization instead.
>
> multiplicity   INTEGER ( default = 0 [unspecified] )
>               spin multiplicity (2s+1). 1 is singlet, 2 for doublet etc.
>               Note that this fixes the final value of the magnetization.
>               if unspecified or a non-zero value is specified in 
> nelup/neldw
>               then multiplicity variable is ignored.
>               Do not specify both multiplicity and tot_magnetization.
>
> tot_magnetization INTEGER ( default = -1 [unspecified] )
>               majority spin - minority spin (nelup - neldw).
>               if unspecified or a non-zero value is specified in 
> nelup/neldw
>               then tot_magnetization variable is ignored.
>               Do not specify both multiplicity and tot_magnetization.
>               YES, there is redundancy! nelup/neldw are enough to specify
>               the spin state. However these variables are not very 
> convenient
>               and will be eliminated from the input in future versions.
>               It is recommended to use either 'multiplicity' or 
> equivalently
>               'tot_magnetization' to specify the spin state.
> -------------------------------------------------------------------------------
> -- 
> Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
> Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513
> Piazza dei Cavalieri 7      I-56126 Pisa, Italy
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