Hi,
It's your own responsibility to make clear what crystal class your system
belongs to.
Do you know the symbol of space group of your system? For your case, if it's
Pxxx,
the system should be simple tetragonal (ibrav=6), if it's Ixxx, it should be
base centered
tetragonal (ibrav=7).
zhou huiqun
@earth sciences, nanjing university, china
----- Original Message -----
From: tian kong
To: PWSCF Forum
Sent: Saturday, June 25, 2011 9:49 PM
Subject: Re: [Pw_forum] how to choose ibrav
yeah, i think you are right. but what really matters is how to set ibrav in
pwscf.
ibrav structure celldm(2)-celldm(6)
6 Tetragonal P (st) celldm(3)=c/a
7 Tetragonal I (bct) celldm(3)=c/asimple tetragonal
(p)
====================
v1 = a(1,0,0), v2 = a(0,1,0), v3 = a(0,0,c/a)
body centered tetragonal (i)
================================
v1 = (a/2)(1,-1,c/a), v2 = (a/2)(1,1,c/a), v3 = (a/2)(-1,-1,c/a).
it seems that: if ibrav=6, then A=B?C. if ibrav=7, then A=B=C.but what i need
is A?B=C. i don't know if i can choose ibrav=6 or 7, and should i need to
change the atoms position after i choose ibrav=6 or 7 ?
>>>>>>>>?this is an email sent by tiankong?
2011/6/24 GAO Zhe <flux_ray12 at 163.com>
In your case, this structure must be simple tetragonal or body centered
tetragonal. Please check your model more carefully from PDF-card or ICSD
database.
P.S.: the choice of ibrav depends on the knowledge of crystallography,
please learn it before you do ab-initio calculation, since symmetry is a very
important and foundamental thing in this area.
--
GAO Zhe
CMC Lab, MSE, SNU, Seoul, S.Korea
At 2011-06-24 15:25:10?"tian kong" <thisisasafeaccount at gmail.com> wrote:
i have read the help document about INPUT_PW.htm again and again, but
since i'm a newbie, i still don't know whice one i should choose. can you help
me?
here is the problem:
A=10, B=C=8, cosAB=cosBC=cosAC=0.
can you tell me ibrav=?
thx a lot !!!
>>>>>>>>?this is an email sent by tiankong?
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