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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>
Thank you very much, I have always visualized the structure using xcrsyden, the
structure seems to be right. But the pwscf always could not find the right
symmetry group(namely R3C), I am afraid that the input position is not
appropriate in some place, unfortunately I couldn't find it so far. You mean the
coordinates should subtract 1 from the original value when it's value
exceed 1 in the crystal unit, that is to say the positon is displaced by
one unit basis vector. So the same reason the 1.038 is equal to 0.038 in
the crystal scheme. Am I right?</FONT></DIV>
<DIV><FONT face=Verdana color=#0000ff size=2></FONT> </DIV>
<DIV><FONT face=Verdana color=#0000ff size=2> Best
regards</FONT></DIV>
<DIV><FONT face=Verdana color=#0000ff size=2> </FONT></DIV>
<DIV><FONT face=Verdana size=2>
<DIV>Hongkien Feng</DIV>
<DIV>Physics department,</DIV>
<DIV>Beijing university of</DIV>
<DIV>aeronautics and astronautics</DIV></FONT></DIV>
<DIV align=left>
<DIV align=left><FONT face=Verdana size=2>
<HR style="WIDTH: 122px; HEIGHT: 2px" SIZE=2>
</FONT></DIV>
<DIV><FONT color=#c0c0c0><FONT face=Verdana size=2>fenghongjian</FONT></DIV>
<DIV><FONT face=Verdana size=2>2007-08-03</FONT></FONT></DIV></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 04:00:20</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>Hi, Feng,</DIV>
<DIV> </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> </DIV>
<DIV>Hope you will find the correct structure.</DIV>
<DIV> </DIV>
<DIV>Best regards,</DIV>
<DIV>Ding</DIV>
<DIV> </DIV>
<DIV>fenghongjian wrote:</DIV>
<DIV> </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 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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<DIV>> </DIV>
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