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["Shtogun, Yaroslav" <yshtogun@cas.usf.edu>]

Hi!
 I also try to optimize the geometry 7_0 CNT but in my case I use default 
value of rprim (1 0 0; 0 1 0; 0 0 1) see my input file and sketch of unit 
cell in attachment. In this case abinit calculates the space group base on 
atoms position. I can advise you use default value of rprim and see what 
happened.  Also, use less value of toldff, your calculation will be faster, 
then you specify more precisely. 

 On the other hand I am confused with ngkpt? 
   Can you explain to my how you choose ngkpt? Why is it 2 2 10, what 
criteria for this?
 
 

Yaroslav Shtogun
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-----Original Message-----
From: 张 [mailto:zhangting@pku.edu.cn] 
Sent: Thursday, April 06, 2006 10:51 AM
To: forum@abinit.org
Cc: zhangting@ele.pku.edu.cn
Subject: [abinit-forum] Why the code can't find a symmetry automatically?

Dear Abinit user:
   
    I'm a beginner of abinit codes. I'm going to do some electron-
phonon coupling calculation of CNTs with the code.When I want to 
optimize the geometric configuration of (5,5) CNT,the program send me 
a warning that it can't find the cell's space group. As a result,the 
optimization job continues with maybe P1 symmetry, and consumes quite 
large memory and time. Now the job is still 
running, I'd like to know hwo to let the code find a space group 
automaticaly? and how to impose a symmetry in the cell manually? Does 
the cell have a P21/M (number 11) space group? I've set the keyword 
spgroup = 11,but it doesn't work...  I'm also afraid that if the 
single point energy is calculated with no symmetry, whether ot not the 
next phonon calculation will be reliable? For there are often 
imaginary frequencies near Gamma point in carbon systems(graphite,CNTs)
    My input file is attached.If there are any other mistakes or 
parameters unsuitable in the input file, don't hesitate to point 
out.thanks a lot 

                                                                    
Zhang Ting
                                                                    
Apr.6th 2006

Attachment: 7_0_1_421.in
Description: 7_0_1_421.in

Attachment: cell.JPG
Description: cell.JPG