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<DIV><FONT face=Verdana color=#0000ff size=2>Dear Ding,</FONT></DIV>
<DIV><FONT face=Verdana color=#0000ff size=2></FONT> </DIV>
<DIV><FONT face=Verdana color=#0000ff
size=2> Under R3c (x y z, z x y, y z x,
y+1/2 x+1/2 z+1/2, x+1/2 z+1/2 y+1/2, z+1/2 y+1/2 x+1/2 with considering the 60
degree of rotation), Therefore the position {<FONT
color=#000000>O(6e)(0.538 </FONT>0.933 0.395) }should be</FONT></DIV>
<DIV><FONT face=Verdana size=2></FONT> </DIV>
<DIV align=left><FONT face=Verdana size=2>
<DIV>> O 0.53800 0.93300 0.39500</DIV>
<DIV>> O 0.39500 0.53800 0.93300</DIV>
<DIV>> O 0.93300 0.39500 0.53800</DIV>
<DIV>> O 1.43300 1.03800 0.89500</DIV>
<DIV>> O 1.03800 0.89500 1.43300</DIV>
<DIV>> O 0.89500 1.43300 1.03800</DIV></FONT></DIV>
<DIV><FONT face=Verdana size=2></FONT> </DIV>
<DIV><FONT face=Verdana size=2>Thank you for your kindly
discussion.</FONT></DIV>
<DIV><FONT face=Verdana size=2></FONT> </DIV>
<DIV><FONT face=Verdana size=2>Best regards</FONT></DIV>
<DIV><FONT face=Verdana size=2>Hongkien Feng</FONT></DIV>
<DIV><FONT face=Verdana size=2> </DIV>
<DIV align=left>
<HR style="WIDTH: 122px; HEIGHT: 2px" SIZE=2>
</DIV></FONT>
<DIV align=left><FONT color=#c0c0c0><FONT face=Verdana
size=2>fenghongjian</FONT></DIV>
<DIV align=left><FONT face=Verdana size=2>2007-08-03</FONT></FONT></DIV>
<DIV><FONT face=Verdana size=2>
<HR>
</FONT></DIV>
<DIV><FONT face=Verdana><FONT size=2><STRONG>发件人：</STRONG> Xunlei
Ding</FONT></FONT></DIV>
<DIV><FONT face=Verdana><FONT size=2><STRONG>发送时间：</STRONG>
2007-08-03 16:39:48</FONT></FONT></DIV>
<DIV><FONT face=Verdana><FONT size=2><STRONG>收件人：</STRONG> PWSCF
Forum</FONT></FONT></DIV>
<DIV><FONT face=Verdana><FONT size=2><STRONG>抄送：</STRONG> </FONT></FONT></DIV>
<DIV><FONT face=Verdana><FONT size=2><STRONG>主题：</STRONG> Re: [Pw_forum] BiFeO3
problem</FONT></FONT></DIV>
<DIV><FONT face=Verdana size=2></FONT> </DIV>
<DIV><FONT face=Verdana size=2>
<DIV>Dear Feng,</DIV>
<DIV> </DIV>
<DIV>There is no difference whether you input 1.038 or 0.038.</DIV>
<DIV>You can try it by using xcrysden to see the structure.</DIV>
<DIV>Now your structrue is:</DIV>
<DIV>> O 0.53800 0.93300 0.39500</DIV>
<DIV>> O 0.39500 0.53800 0.93300</DIV>
<DIV>> O 0.93300 0.39500 0.53800</DIV>
<DIV>> O 1.43300 1.03800 0.89500</DIV>
<DIV>> O 1.03800 0.89500 1.43300</DIV>
<DIV>> O 0.89500 1.43300 1.03800</DIV>
<DIV>But why not:</DIV>
<DIV>O 0.53800 0.93300 0.39500</DIV>
<DIV>O 0.39500 0.53800 0.93300</DIV>
<DIV>O 0.93300 0.39500 0.53800</DIV>
<DIV>O 1.03800 1.43300 0.89500</DIV>
<DIV>O 0.89500 1.03800 1.43300</DIV>
<DIV>O 1.43300 0.89500 1.03800</DIV>
<DIV>I am not familar with BiFeO3 and R3c. So I am not sure about that.</DIV>
<DIV> </DIV>
<DIV>Another question is: whether R3c symmetry is included in PWSCF, or</DIV>
<DIV>whether "c" can be recognized by PWSCF.</DIV>
<DIV> </DIV>
<DIV>Best regards,</DIV>
<DIV>Ding</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>fenghongjian wrote:</DIV>
<DIV> </DIV>
<DIV>> Dear Ding,</DIV>
<DIV>> Thank you very much, I have always visualized the structure using</DIV>
<DIV>> xcrsyden, the structure seems to be right. But the pwscf always could</DIV>
<DIV>> not find the right symmetry group(namely R3C), I am afraid that the</DIV>
<DIV>> input position is not appropriate in some place, unfortunately I</DIV>
<DIV>> couldn't find it so far. You mean the coordinates should subtract 1</DIV>
<DIV>> from the original value when it's value exceed 1 in the crystal unit,</DIV>
<DIV>> that is to say the positon is displaced by one unit basis vector. So</DIV>
<DIV>> the same reason the 1.038 is equal to 0.038 in the crystal scheme. Am</DIV>
<DIV>> I right?</DIV>
<DIV>> Best regards</DIV>
<DIV>> Hongkien Feng</DIV>
<DIV>> Physics department,</DIV>
<DIV>> Beijing university of</DIV>
<DIV>> aeronautics and astronautics</DIV>
<DIV>> ------------------------------------------------------------------------</DIV>
<DIV>> fenghongjian</DIV>
<DIV>> 2007-08-03</DIV>
<DIV>> ------------------------------------------------------------------------</DIV>
<DIV>> *发件人：* Xunlei Ding</DIV>
<DIV>> *发送时间：* 2007-08-03 04:00:20</DIV>
<DIV>> *收件人：* PWSCF Forum</DIV>
<DIV>> *抄送：*</DIV>
<DIV>> *主题：* Re: [Pw_forum] BiFeO3 problem</DIV>
<DIV>> Hi, Feng,</DIV>
<DIV>> In crystal unit, 1.433 equals to 0.433. So that's not the reason for</DIV>
<DIV>> your problem.</DIV>
<DIV>> And just setting the unit to "alat" is totally wrong.</DIV>
<DIV>> My suggestion is to use xcrysden to check the structure to see whether</DIV>
<DIV>> it is the same as you thought.</DIV>
<DIV>> Hope you will find the correct structure.</DIV>
<DIV>> Best regards,</DIV>
<DIV>> Ding</DIV>
<DIV>> fenghongjian wrote:</DIV>
<DIV>> > Dear PWSCF users,</DIV>
<DIV>>
> I'm trying to calculate the electronic properties of rhombohedral</DIV>
<DIV>> > BiFeO3 under R3C</DIV>
<DIV>>
> symmetry group. The wychoff position is Bi(2b)(0 0 0),Fe(2a)(0.221</DIV>
<DIV>> > 0.221 0.221),O(6e)(0.538</DIV>
<DIV>>
> 0.933 0.395), hence under R3C group symmetry the atomic position</DIV>
<DIV>> should be</DIV>
<DIV>> > Bi 0.00000 0.00000 0.00000</DIV>
<DIV>> > Bi 0.50000 0.50000 0.50000</DIV>
<DIV>> > Fe 0.22100 0.22100 0.22100</DIV>
<DIV>> > Fe 0.72100 0.72100 0.72100</DIV>
<DIV>> > O 0.53800 0.93300 0.39500</DIV>
<DIV>> > O 0.39500 0.53800 0.93300</DIV>
<DIV>> > O 0.93300 0.39500 0.53800</DIV>
<DIV>> > O 1.43300 1.03800 0.89500</DIV>
<DIV>> > O 1.03800 0.89500 1.43300</DIV>
<DIV>> > O 0.89500 1.43300 1.03800</DIV>
<DIV>>
> When I set the ATOMIC_POSITIONS in alat unit the code gave no</DIV>
<DIV>> > symmetry, and the code</DIV>
<DIV>>
> produced wrong symmertry ( not R3c group) with the ATOMIC_POSITIONS in</DIV>
<DIV>> > crystal unit.</DIV>
<DIV>>
> Acturally in crystal unit the triplet coordinates should be less than</DIV>
<DIV>> > 1, but in my case the</DIV>
<DIV>>
> 1.433 was obviously wrong, but O(6e)(0.538 0.933 0.395) under R3C will</DIV>
<DIV>> > definitely produce</DIV>
<DIV>>
> the value above. I have encountered this problem for a long time,</DIV>
<DIV>> > could anyone point the</DIV>
<DIV>>
> wrong place in my case? Any sugestions will be very appreciated.</DIV>
<DIV>>
> My input file was pasted below:</DIV>
<DIV>> > &control</DIV>
<DIV>> > calculation='scf'</DIV>
<DIV>> > restart_mode='from_scratch',</DIV>
<DIV>> > verbosity='high',</DIV>
<DIV>> > prefix='bifo',</DIV>
<DIV>> > pseudo_dir='./',</DIV>
<DIV>> > outdir='./'</DIV>
<DIV>> > /</DIV>
<DIV>> > &system</DIV>
<DIV>>
> ibrav= 5, celldm(1)= 10.6427, celldm(4)= 0.5, nat= 10, ntyp= 3,</DIV>
<DIV>> > ecutwfc=35.0</DIV>
<DIV>> > occupations = 'fixed'</DIV>
<DIV>> > degauss=0.00</DIV>
<DIV>> > nbnd=100</DIV>
<DIV>> > lda_plus_u=.true. Hubbard_U(2)=5,</DIV>
<DIV>> > nspin=2,multiplicity=5,</DIV>
<DIV>> > /</DIV>
<DIV>> > &electrons</DIV>
<DIV>> > mixing_beta=0.3,</DIV>
<DIV>> > diagonalization='cg'</DIV>
<DIV>> > /</DIV>
<DIV>> > ATOMIC_SPECIES</DIV>
<DIV>> > Bi 208.98 Bi.pbe-d-mt.UPF</DIV>
<DIV>> > Fe 55.847 Fe.pbe-sp-van_ak.UPF</DIV>
<DIV>> > O 15.999 O.pbe-van_ak.UPF</DIV>
<DIV>> > ATOMIC_POSITIONS {alat}</DIV>
<DIV>> > Bi 0.00000 0.00000 0.00000</DIV>
<DIV>> > Bi 0.50000 0.50000 0.50000</DIV>
<DIV>> > Fe 0.22100 0.22100 0.22100</DIV>
<DIV>> > Fe 0.72100 0.72100 0.72100</DIV>
<DIV>> > O 0.53800 0.93300 0.39500</DIV>
<DIV>> > O 0.39500 0.53800 0.93300</DIV>
<DIV>> > O 0.93300 0.39500 0.53800</DIV>
<DIV>> > O 1.43300 1.03800 0.89500</DIV>
<DIV>> > O 1.03800 0.89500 1.43300</DIV>
<DIV>> > O 0.89500 1.43300 1.03800</DIV>
<DIV>> > K_POINTS {automatic}</DIV>
<DIV>> > 8 8 8 0 0 0</DIV>
<DIV>> > Best Regards,</DIV>
<DIV>> ></DIV>
<DIV>> > Hongkien Feng</DIV>
<DIV>> > Physics department,</DIV>
<DIV>> > Beijing university of</DIV>
<DIV>> > aeronautics and astronautics</DIV>
<DIV>>
> ------------------------------------------------------------------------</DIV>
<DIV>> > fenghongjian</DIV>
<DIV>> > 2007-08-02</DIV>
<DIV>> ></DIV>
<DIV>>
>------------------------------------------------------------------------</DIV>
<DIV>> ></DIV>
<DIV>> >_______________________________________________</DIV>
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href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</A></DIV>
<DIV>> ></DIV>
<DIV>> ></DIV>
<DIV>> _______________________________________________</DIV>
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href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</A></DIV>
<DIV>></DIV>
<DIV>>------------------------------------------------------------------------</DIV>
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