On Thursday, December 17, 2015 03:31:02 PM yin li wrote: > 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.
In principle you should get exactly zero, it is a mathematical condition which is quite straightforward to impose. I only saw non-zero frequency after sum rule when also effective charges are present. In any case, these are low enough to be considered zero, except in some very specific corner case. > # 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. Is your system an isolated molecule, or a nanocluster? Because the zero-dim acoustic sum rule is only suited for these cases, and must no be used for anything else. -- Dr. Lorenzo Paulatto IdR @ IMPMC -- CNRS & Université Paris 6 +33 (0)1 44 275 084 / skype: paulatz http://www.impmc.upmc.fr/~paulatto/ 23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
