[Pw_forum] Phonon DOS

[Eyvaz Isaev]

Dear Subhradip,

I assume it will not affect for your calculations if
you have a metallic system. 
But it is very important for polar semiconductors
where 
splitting of optical modes at the \Gamma point is not
possible without applying electric field via
calculation of macroscopic dielectric constant.
The error means that electric field is not included. 

A reason for the message might be you did not 
mention degauss and ngauss parameters for SCF
calculations (for old versions). For the new version
there should be three paremeters:  occupations,
smearing, degauss (in "system" section). If there are
not, your system is assumed to be semiconductor type.

Besides, I remember my promise. I will do that soon.  

Regards,
Eyvaz.
Theoretical Physics Department
Moscow Steel and Alloys Institute

--- Subhradip Ghosh <subhra at physics.rutgers.edu>
wrote:
> Hi,
> 
> I am trying to compute Phonon DOS using the code
> matdyn.f90. I found that
> it worked for an insulator but in my case the system
> is metallic and while
> I ran the code there is some output generated
> alongwith an error message
> 
>
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      from matdyn : error #        -1
>      non-analytic term for q=0 missing !
> 
>
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> I traced it back to the code and found that this
> error message pops up in
> case we have no dielectric tensor(probably) written
> in the real-space
> force constant
> file. There is a logical switch in the force
> constant file which comes out
> to be F in my case and therefore there are no
> entries of the variable
> epsil. I have no idea what the remedy is? Is it a
> serious error or should
> I ignore it?
> 
> Thanks in advance,
> 
> Subhradip
> 
> PS: My system is not a simple metal, rather a
> metallic alloy.
> 
>
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> 		Condensed matter theory group
> 	        Department of Physics and Astronomy
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