Maybe your 441 cm-1 mode has a large admixture of a rotational mode?
This may happen if the supercell is not large enough
Paolo
On 11/1/2025 12:55 AM, Tang, Weilun [M S E] via users wrote:
Dear Quantum Espresso users,
I made a phonon calculation for an isolated molecule using acoustic sum
rule *asr='zero-dim'. *Then, I compared the phonon modes before and
after applying the acoustic sum rule. I noticed that there is a mode
that has a huge change in frequency, as shown below. More specifically,
the *441.1 cm-1* mode seems to be shifted to *115.30 cm-1 *after
applying the acoustic sum rule. Is this normal?
For this calculation, I used lower threshold: forc_conv_thr = 1.0D-6,
etot_conv_thr = 1.0D-6, conv_thr = 1.D-14 for pw.x. And for phx, I use
tr2_ph=1.0d-18.
-------------------------------------------------------------
Below is phonon modes from ph.x:
Mode symmetry, D_3h (-62m) point group:
freq ( 1- 1) = -27.8 [cm-1] --> A'_2
freq ( 2- 3) = 65.6 [cm-1] --> E'' R
freq ( 4- 4) = 103.9 [cm-1] --> A''2 I
freq ( 5- 6) = 120.4 [cm-1] --> E'' R
freq ( 7- 8) = 146.2 [cm-1] --> E' I+R
freq ( 9- 10) = 188.8 [cm-1] --> E' I+R
freq ( 11- 11) = 367.1 [cm-1] --> A'_1 R
freq ( 12- 13) = 430.7 [cm-1] --> E' I+R
freq ( 14- 14) = 441.1 [cm-1] --> A''2 I
freq ( 15- 15) = 461.4 [cm-1] --> A'_2
freq ( 16- 17) = 631.9 [cm-1] --> E'' R
freq ( 18- 18) = 776.4 [cm-1] --> A''2 I
freq ( 19- 20) = 801.0 [cm-1] --> E' I+R
freq ( 21- 21) = 907.1 [cm-1] --> A'_1 R
freq ( 22- 22) = 1101.1 [cm-1] --> A'_2
freq ( 23- 24) = 1150.0 [cm-1] --> E' I+R
freq ( 25- 25) = 1189.0 [cm-1] --> A'_1 R
freq ( 26- 27) = 1337.2 [cm-1] --> E' I+R
----------------------------------------------------------------
Below is output from dynmat.x
Reading Dynamical Matrix from file dmat.ttc
...Force constants read
...epsilon and Z* read
...Raman cross sections read
Acoustic Sum Rule: || Z*(ASR) - Z*(orig)|| = 1.029894E+00
Acoustic Sum Rule: ||dyn(ASR) - dyn(orig)||= 2.701556E-01
A direction for q was not specified:TO-LO splitting will be absent
Polarizability (A^3 units)
multiply by 0.759092 for Clausius-Mossotti correction
262.517180 -0.000000 -0.000000
-0.000000 262.517180 -0.000000
0.000000 0.000000 57.305445
IR activities are in (D/A)^2/amu units
Raman activities are in A^4/amu units
multiply Raman by 0.576221 for Clausius-Mossotti correction
# mode [cm-1] [THz] IR Raman depol.fact
1 -0.00 -0.0000 0.0000 16.3234 0.7500
2 -0.00 -0.0000 0.0000 3355.0146 0.7500
3 -0.00 -0.0000 0.0000 1478.4689 0.7500
4 0.00 0.0000 0.0000 285.5435 0.7500
5 0.00 0.0000 0.0000 873.4000 0.7500
6 0.00 0.0000 0.0000 1623.8289 0.7500
7 73.38 2.1998 0.0000 696.8190 0.7500
8 73.38 2.1998 0.0000 696.8152 0.7500
9 115.30 3.4567 0.2787 0.0000 0.7500
10 177.24 5.3134 1.7092 44473.2909 0.7500
11 177.24 5.3134 1.7092 44473.2914 0.7500
12 367.09 11.0050 0.0000 11288132.4685 0.1106
13 436.75 13.0934 0.2992 3721.4221 0.7500
14 436.75 13.0934 0.2992 3721.4231 0.7500
15 462.38 13.8617 0.0000 0.0004 0.7500
16 631.59 18.9347 0.0000 13677.2759 0.7500
17 631.59 18.9347 0.0000 13677.2842 0.7500
18 778.46 23.3377 0.0792 0.0000 0.7500
19 802.57 24.0605 12.9665 1800840.5786 0.7500
20 802.57 24.0605 12.9665 1800840.5109 0.7500
21 907.11 27.1945 0.0000 8355726.6168 0.1191
22 1101.10 33.0101 0.0000 0.0000 0.7500
23 1150.13 34.4801 26.2055 16251271.1703 0.7500
24 1150.13 34.4801 26.2055 16251270.4526 0.7500
25 1189.02 35.6458 0.0000 16979.5440 0.2674
26 1337.59 40.1000 27.2231 16068754.7864 0.7500
27 1337.59 40.1000 27.2231 16068754.1344 0.7500
--------------------------------------------------------------------------------------------------------
Below is my input file for pw.x
&CONTROL
calculation = "scf",
prefix = "ttc",
pseudo_dir = "/home/weilunt/pseudopotential/norm_conserving/pz",
outdir = "./tmp",
forc_conv_thr = 1.0D-6,
etot_conv_thr = 1.0D-6,
/
&SYSTEM
assume_isolated = 'martyna-tuckerman',
ibrav = 4,
A = 17.2,
C = 10,
nat = 9,
ntyp = 3,
ecutwfc = 80.D0, !better 120
tot_charge = -3,
occupations = 'fixed',
/
&ELECTRONS
conv_thr = 1.D-14,
mixing_beta = 0.7,
electron_maxstep = 200,
/
&IONS
/
ATOMIC_SPECIES
S 32.070 S.pz-hgh.UPF
N 14.007 N.pz-hgh.UPF
C 12.010 C.pz-hgh.UPF
ATOMIC_POSITIONS (angstrom)
S 0.0000000000 -3.0749791762 -0.0000000000
S -2.6627598154 1.5374395881 -0.0000000000
S 2.6627598154 1.5374395881 0.0000000000
N 1.1913527585 -0.6879250817 -0.0000000000
N -1.1913527585 -0.6879250817 0.0000000000
N 0.0000000000 1.3757501635 0.0000000000
C 0.0000000000 -1.3240902237 -0.0000000000
C -1.1466139383 0.6620951119 0.0000000000
C 1.1466139383 0.6620951119 0.0000000000
K_POINTS (automatic)
1 1 1 0 0 0
-----------------------------------------------------------------------------------------
Thank you for your time and your help in advance,
Weilun Tang
_______________________________________________________________________________
The Quantum ESPRESSO Foundation stands in solidarity with all civilians
worldwide who are victims of terrorism, military aggression, and indiscriminate
warfare.
--------------------------------------------------------------------------------
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list [email protected]
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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216
_______________________________________________________________________________
The Quantum ESPRESSO Foundation stands in solidarity with all civilians
worldwide who are victims of terrorism, military aggression, and indiscriminate
warfare.
--------------------------------------------------------------------------------
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
