Dear Peter Blaha Sir,<div><br></div><div> Thank you very much for your reply. I have understand what you have said and will try to implement the same. Yes it should solve the problem. Thank you sir, thank you very much!!....</div>
<div><br></div><div>with best regards,</div><div>Shamik Chakrabarti<br><br><div class="gmail_quote">On Sat, Oct 23, 2010 at 12:17 PM, Peter Blaha <span dir="ltr"><<a href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Then it simply means, that after min_lapw your atoms arrived at positions, which made them nearly equivalent, so that sgroup does not know within its accuracy limits if two atoms are equivalent or not.<br>
<br>
Eventually "correct" positions manually, eg. setting atoms at<br>
0.50002 to 0.50000 and so on.<br>
<br>
Am 23.10.2010 08:42, schrieb shamik chakrabarti:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im">
Dear Peter Blaha Sir,<br>
I am using wien2k_08. No it is not an<br>
hexagonal lattice. Actually the space group is unknown. We have taken a<br>
structure A2BCO4 which has space group Pnma and then *replace atom C<br>
with atom D *considering *primitive space group*. We have used the<br>
atomic coordinates and lattice constants of A2BCO4. But we have made all<br>
the atoms inequivalent in the new material A2BDO4 by considering<br>
primitive space group. It was done as we *do not want to include the<br>
symmetry constraints* for the atoms of this new material as A2BDO4 may<br>
have some different structure than A2BCO4. We want to see if A2BDO4<br>
structure is feasible or not and infact DFT has found a structure with<br>
minimum energy and minimum force on the atoms.<br>
<br>
with best regards,<br>
Shamik Chakrabarti<br>
On Sat, Oct 23, 2010 at 11:48 AM, Peter Blaha<br></div><div><div></div><div class="h5">
<<a href="mailto:pblaha@theochem.tuwien.ac.at" target="_blank">pblaha@theochem.tuwien.ac.at</a> <mailto:<a href="mailto:pblaha@theochem.tuwien.ac.at" target="_blank">pblaha@theochem.tuwien.ac.at</a>>> wrote:<br>
<br>
Are you using WIEN2k_10 ??? It should not happen anymore.<br>
<br>
Hexagonal lattice ??? min_lapw could have produced atomic<br>
positions, which are not completely equivalent anymore (like<br>
0.3333333 and 0.666666) because of rounding errors.<br>
<br>
Check your atomic positions manually.<br>
<br>
Am 23.10.2010 06:22, schrieb shamik chakrabarti:<br>
<br>
Dear wien2k users,<br>
<br>
we have done structure optimization<br>
(both<br>
volume and force) of a A2BCO4 type material. After optimization the<br>
maximum force on an atom is *2.036 mRy/a.u.* After optimization<br>
if we<br>
view the structure with xcrysden we can see that some atoms remain<br>
unbonded i.e. one or two free atom and the rest of the structure is<br>
connected through bond. Now my questions are:<br>
<br>
(1) Can such a structure be stable although DFT has<br>
able to<br>
found a solution in which the energy of the unit cell and forces<br>
on the<br>
atoms are minimum?<br>
<br>
(2) When I take this optimized struct file and tried to<br>
initilize and run a SCF with this struct file, after *x sgroup*<br>
command<br>
it will show :<br>
*Accuracy problem. Please run with different tolerance (x sgroup<br>
-settol<br>
.00000100)*<br>
*<br>
*<br>
Now if we ignore this problem or we run the command x<br>
sgroup -settol 0.00000100, irrespective of that all the atoms got<br>
deleted after x symmetry command!!<br>
<br>
So, my question is whether this optimized struct<br>
file is<br>
not feasible or is their any way to remove this accuracy problem?<br>
<br>
any response will be very helpful for us. Thanking you,<br>
<br>
with regards,<br>
<br>
<br>
--<br>
Shamik Chakrabarti<br>
Research Scholar<br>
Dept. of Physics & Meteorology<br>
Material Processing & Solid State Ionics Lab<br>
IIT Kharagpur<br>
Kharagpur 721302<br>
INDIA<br>
<br>
<br>
<br>
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<br>
--<br>
Peter Blaha<br>
Inst.Materials Chemistry<br>
TU Vienna<br>
Getreidemarkt 9<br>
A-1060 Vienna<br>
Austria<br>
+43-1-5880115671<br>
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<br>
<br>
<br>
<br>
--<br>
Shamik Chakrabarti<br>
Research Scholar<br>
Dept. of Physics & Meteorology<br>
Material Processing & Solid State Ionics Lab<br>
IIT Kharagpur<br>
Kharagpur 721302<br>
INDIA<br>
<br>
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</div></blockquote><div><div></div><div class="h5">
<br>
-- <br>
Peter Blaha<br>
Inst.Materials Chemistry<br>
TU Vienna<br>
Getreidemarkt 9<br>
A-1060 Vienna<br>
Austria<br>
+43-1-5880115671<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Shamik Chakrabarti<br>Research Scholar<br>Dept. of Physics & Meteorology<br>Material Processing & Solid State Ionics Lab<br>IIT Kharagpur<br>Kharagpur 721302<br>
INDIA<br>
</div>