[QE-users] Acoustic Sum Rule Frequency Question
Paolo Giannozzi
paolo.giannozzi at uniud.it
Sat Nov 1 18:34:22 CET 2025
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
>
>
>
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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216
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