is your system 0-dim ? is it fully relaxed ?
stefano
On 17/12/2015 15:31, yin li wrote:
Dear QE community,
I wonder if there is a rule to choose acoustic sum rule. I set very
tight convergence criterion for both pw.x (conv_thr = 1.0D-10) and
ph.x(tr2_ph=1.0d-16).
When I applied asr="simple", the frequencies of the first 3 modes are
not equal to zero, but a relatively small negative value. The
low-frequency modes are affected, and there is no change in frequency
number of high-frequency modes.
# mode [cm-1] [THz] IR
1 -1.27 -0.0381 0.0000
2 -1.02 -0.0306 0.0000
3 -0.48 -0.0143 0.0000
4 50.74 1.5212 0.0042
5 66.71 1.9999 0.0031
6 76.72 2.3000 0.1024
7 91.30 2.7372 0.0605
8 92.44 2.7712 0.2996
9 102.29 3.0666 0.2928
10 107.09 3.2105 0.0402
11 113.55 3.4043 0.3288
12 117.59 3.5252 0.5163
13 133.35 3.9977 0.0394
14 136.70 4.0981 0.2142
15 144.03 4.3179 0.4547
16 158.41 4.7490 0.0742
If I employed asr="zero-dim" , the frequencies of the first 6 modes
all become 0. But I found the frequencies of all the modes, even
high-frequency modes, were varied.
# mode [cm-1] [THz] IR
1 -0.00 -0.0000 0.0000
2 -0.00 -0.0000 0.0000
3 -0.00 -0.0000 0.0000
4 -0.00 -0.0000 0.0000
5 -0.00 -0.0000 0.0000
6 0.00 0.0000 0.0000
7 40.75 1.2216 0.0265
8 68.45 2.0520 0.1827
9 82.84 2.4836 0.1281
10 95.99 2.8778 0.2143
11 108.98 3.2671 0.3284
12 113.25 3.3951 0.4248
13 117.89 3.5342 0.2717
14 126.27 3.7854 0.0136
15 136.33 4.0872 0.3745
I am specially interested in the low-frequency region (1-4 THz). How
could I select acoustic sum rule correctly?
Thank you very much in advance!
Best Regards,
Yin
------------------------------------------------------------------------
Dr. Yin Li
Department of Biophysics,Medical School, University of Pecs,
No.12 Szigeti Street, Pecs, H-7624, HUNGARY
Phone: +36-72-535271/36271
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