[Pw_forum] PWscf can not find out symmetry operations!!!

[英利 牛]

Dear all,
  I am calculate properties of diamond
surface(001),the lattice parameters of the slab is :
2.5221A,5.0442A,16.0253A,90,90,90
after atoms relax ,the atom positions(crystal) are:
C     0.24978  -0.11238   0.21129 

C     0.24980   0.60988   0.21129 

C     0.74978  -0.01422   0.17583 

C     0.74980   0.51175   0.17582 

C     0.74981   0.24879   0.13029 

C     0.74981   0.74881   0.11624 

C     0.24982   0.24883   0.07780 

C     0.24982   0.74885   0.07061 

C     0.24984  -0.00014   0.02461 

C     0.24984   0.49787   0.02461 

C     0.74985  -0.00211  -0.02461 

C     0.74986   0.49988  -0.02461 

C     0.74987   0.24889  -0.07061 

C     0.74987   0.74888  -0.07780 

C     0.24987   0.24889  -0.11624 

C     0.24988   0.74888  -0.13029 

C     0.24990   0.01186  -0.17582 

C     0.24987   0.48589  -0.17583 

C     0.74990   0.11000  -0.21129 

C     0.74987   0.38773  -0.21129 


but PWscf can not find any symmetry operations of the
system.
I setup the struct and use Material Studio find 8
space group operations include inversion! The
tolerance is 0.01A.

Then I read PW manual:

the number of significant figures in the atomic
positions is not large enough. In file PW/eqvect.f90,
the variable accep is used to decide whether a
rotation is a symmetry operation. Its current value
(10-5 ) is quite strict: a rotated atom must coincide
with another atom to 5 significant digits. You may
change the value of accep and recompile.

I change accep from 1.0d-5 to 1.0d-2 then to 1.0d-1
,but PWscf still find no symmetry. 

What should I do? 
Why pwscf choose 1.0d-5,so strict?


	

	
		
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