[Wien] Structure problem in NiAs-type

[王静]

Hi, there!
   When I tried to calculate some properties about NiAs, there are some problems.
(1)	I uploaded a NiAs.cif with symmetry (space group P63/mmc, No.194). Everything goes well. Nevertheless, when I uploaded the structure without symmetry, say, space group P1, No. 1, the symmetry found by WIEN is in space group Cmcm, No.63. This is weird. 
(2)	Using the P1 symmetry, I tried to substitute half of the Ni by other atoms, the symmetry found by WIEN is C2/m, No. 12. Then I restart the StructGen. When “x sgroup -up” is executed, the following message is met,

Error lat==HEXAGONAL in det_pgrp()
Accuracy problem. Please run with different tolerance (x sgroup -settol .00000100)
Error lat==HEXAGONAL in det_pgrp()
0.000u 0.000s 0:00.00 0.0%	0+0k 0+0io 0pf+0w
error: command   /software/wien2k/sgroup -wi NiAs.struct -wo NiAs.struct_sgroup  -set-TOL=0.00001   failed

One the other hand, by using MS, I found the half substituted case is in space group P-3M1, No 164. I think it might be necessary to transfer the internal atomic position to be rhombohedral form. Therefore, I transferred the internal positions. 
                      Hexagonal position        rhombohedral position 
Ni                        (0 0 0)                        (0 0 0)
Atoms substituted Ni     (0 0 0.5)                    (0.5 0.5 0.5)
As                      (1/3 2/3 0/25)          (0.58334 0.58333 0.58333)

The two positions (0.5 0.5 0.5) and (0.58333 0.58333 0.58333) turn out to be close to each other, giving RMT as small as 0.5 for As. 

Could someone help me out? Thanks very much!


                     Wang Jing
　　　　　　　　wangjingjing at ciac.jl.cn
　　　　　　　　　　2012-07-01