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<div class="moz-cite-prefix">dear Alexander,<br>
<br>
the grid correspond to a 8x8x8 supercell (or rather to the FFT
of a 8x8x8 q-point grid ... which is the same) <br>
<br>
atomic pairs are specified by the indices of the two atoms in
the unit cell plus the direct lattice vector connecting the two
cells in which they are located with two important details to be
considered<br>
1) the origin is the 1,1,1 element of the list<br>
2) the IFC are obtained by a FFT from the dynamical matrices
of the q-point grid and are therefore written assuming 8 8 8
periodicity (in the present case)<br>
the corresponding relevant real space vectors vectors are
therefore given by<br>
<span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
r(i) = (n1-1)*at(i,1)+(n2-1)*at(i,2)+(n3-1)*at(i,3) + their
periodic refolding to points nearest the origin </span><br>
a few examples should clarify:<br>
1 1 1 -> r = 0<br>
2 1 1 -> r = a1<br>
8 1 1 -> r = -a1<br>
<br>
the routine weight play the fundamental role of trimming the
vector in such a way the only the points inside the wigner-seitze<br>
cell of the supercell contribute<br>
weight (r) = 1 if r is inside the WS cell<br>
weight (r) = 0 if r is ouside the WS cell<br>
weight (r) = 1/(n+1) if r is on the surface of the WS cell
where n is the number of planes that pass through it<br>
<br>
stefano<br>
<br>
On 11/06/2014 06:14 PM, Kvasov Alexander wrote:<br>
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<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">Dear
All,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">My
question is: how the supercell (which is used by q2r and
matdyn) is specified? If anybody has any information about
this I would highly appreciate.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">“fltau”
option of matdyn gives atomic positions only for 1 cell and
not for N1xN2xN3 supercell.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">Apparently,
there are some tricks… for example, here one has some IFCs
for 8x8x8 grid of SrTiO3<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">...<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
8 8 8<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
1 1 1 1<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
1 1 1 5.72142674655E-02<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
2 1 1 -1.06343912107E-02<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
3 1 1 1.01649714042E-04<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
</span><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black"
lang="FR-CH">4 1 1 4.15611567060E-06<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black"
lang="FR-CH"> 5 1 1 -6.46046533014E-06<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black"
lang="FR-CH"> 6 1 1 4.15611567060E-06<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black"
lang="FR-CH"> 7 1 1 1.01649714042E-04<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
8 1 1 -1.06343912107E-02<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">...<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">1.
first, IFC values decries with N1 and then increase, so they
have to be shuffled<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">2.
second, it seems SUBROUTINE setupmat and frc_blk is the
right place to look for this<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">…<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">DO
na=1, nat<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
DO nb=1, nat<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
total_weight=0.0d0<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
DO n1=-2*nr1,2*nr1<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
DO n2=-2*nr2,2*nr2<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
DO n3=-2*nr3,2*nr3<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
!<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
! SUM OVER R VECTORS IN THE SUPERCELL - VERY VERY SAFE
RANGE!<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
!<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
DO i=1, 3<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
r(i) = n1*at(i,1)+n2*at(i,2)+n3*at(i,3)<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">
END DO<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">…<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">but
summation goes from -2N to 2N, which is not clear for me.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">3.
what is “weight” in SUBROUTINE setupmat and frc_blk<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black">If
anybody could explain what is going on here it would be
great!<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Cambria",serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB">Sincerely
yours,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB">Alexander
Kvasov<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB">Scientist<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB"
lang="FR-CH">Ceramics Laboratory (LC)<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB"
lang="FR-CH">École Polytechnique Fédérale de Lausanne (EPFL)<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB"
lang="FR-CH"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB">Phone:
+41 21 693 5805<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB">Address:<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB">EPFL
STI IMX LC<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB">MXD
220 (Bâtiment MXD) Station 12<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Cambria",serif;color:black;mso-fareast-language:EN-GB">1015
Lausanne, Switzerland<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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