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<div>Dear Eyvaz,
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Many thanks your suggestions or comments.
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>This one can be done using matdyn.x, too.
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Can you give me example file to finish LO-TO spliting using matdyn.x? I noticed that for insulator, by default, ph.x firstly calculate electric field and effective charges. Why?
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</FONT><FONT color=#444444>> If the difference in between number of atoms not too much, I would prefer hexagonal.
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There are much difference in between nubmers of atoms. There are 30 atoms in unit cell. But in its primitive cell,
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the number of atoms is only 10.
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By the way, now I can obtain dielectriic constants (high frequency dielectric constants) and effective charges, but I don't know how to get static dielectrin constant and polar charges? can you give me some suggestions? Thanks a lot.
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Best regards,
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Yanling Li,
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Institute of solid states physics, CAS, China.
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-------------------------------------------------------------------------
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>>Dear Li,
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<BR>
>>This one can be done using matdyn.x, too.
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>>My system has hexagonal symmetry and its primitive cell is rhombohedral.
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>>If the difference in between number of atoms not too much, I would prefer hexagonal, as it has higher symmetry >>and this will make things easier.
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>>From matdyn.f90:
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>
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</FONT><FONT color=#444444>> ! Then, if (.not.dos) :
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</FONT><FONT color=#444444>> ! nq number of q-points
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</FONT><FONT color=#444444>> ! (q(i,n), i=1,3) nq q-points in 2pi/a units
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</FONT><FONT color=#444444>> ! If q = 0, the direction qhat (q=>0) for the non-analytic part
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</FONT><FONT color=#444444>> ! is extracted from the sequence of q-points as follows:
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</FONT><FONT color=#444444>> ! qhat = q(n) - q(n-1) or qhat = q(n) - q(n+1)
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</FONT><FONT color=#444444>> ! depending on which one is available and nonzero.
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</FONT><FONT color=#444444>> ! For low-symmetry crystals, specify twice q = 0 in the list
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</FONT><FONT color=#444444>> ! if you want to have q = 0 results for two different directions
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</FONT><FONT color=#444444>> !
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</FONT><FONT color=#444444>> Anyway, you should specify 2 directions like
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</FONT><FONT color=#444444>> x(1) y(1) z(1)
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</FONT><FONT color=#444444>> ........
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</FONT><FONT color=#444444>> x(N-1) y(N) z(N)
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>0 0 0 !!!!! Gamma point x(N)=0 y(N)=0 z(N)=0
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>x(N+1) y(N+1) z(N+1)
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</FONT><FONT color=#444444>> .........
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</FONT><FONT color=#444444>> x(M) y(M) z(M)
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</FONT><FONT color=#444444>> For a hexagonal lattice you could try A (00z) --</FONT><FONT color=#444444>> G(000) --</FONT><FONT color=#444444>> K(-1/3,2/3,0), as example.
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</FONT><FONT color=#444444>> Hope this helps.
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</FONT><FONT color=#444444>> Bests, Eyvaz.
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>--- On Thu, 4/16/09, Li YL <<A href=mailto:ylli@theory.issp.ac.cn>ylli@theory.issp.ac.cn</A></FONT><FONT color=#444444>> wrote:
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</FONT><FONT color=#444444>> Dear all users,
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</FONT><FONT color=#444444>>
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</FONT><FONT color=#444444>> Now I've a question on the polar materials. In order to
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</FONT><FONT color=#444444>> get LO-TO splitting, you know, we need to use dynmat.x. In
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</FONT><FONT color=#444444>> the input file for dynmat.x, we need input q(1), q(2), and
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</FONT><FONT color=#444444>> q(3), that is, the propagation direction. I don't know
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</FONT><FONT color=#444444>> how to choose this direction. My system has hexagonal
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</FONT><FONT color=#444444>> symmetry and its primitive cell is rhombohedral.
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</FONT><FONT color=#444444>> Any suggestions are welcome. Thanks in advance.
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</FONT><FONT color=#444444>>
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</FONT><FONT color=#444444>> Bests,
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</FONT><FONT color=#444444>>
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</FONT><FONT color=#444444>> Yanling Li,
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</FONT><FONT color=#444444>>
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</FONT><FONT color=#444444>> Institute of Solid states physics, CAS, P. R. China.
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Re: [Pw_forum] propagation direction in the input file
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