[QE-users] Acoustic Sum Rule Frequency Question

Sat Nov 1 11:42:08 CET 2025

Hi Weilum, 

I don't have the answer for your question exactly, but could you also share your full elph.in file? 

Thanks, 
Shubham 

From: "Tang, Weilun [M S E] via users" <users at lists.quantum-espresso.org> 
To: "users" <users at lists.quantum-espresso.org> 
Sent: Friday, October 31, 2025 11:55:28 PM 
Subject: [QE-users] Acoustic Sum Rule Frequency Question 

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 

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