[ase-users] vibration analysis with reaxff

[Avakyan L.A.]

Hello, Claudio,

I got have obtained the following:
CHONSSiPtZrNiCuCo.reax
---------------------
   #    meV     cm^-1
---------------------
   0    0.0i      0.0i
   1    0.0       0.0
   2    0.0       0.0
   3  160.5    1294.4
   4  161.5    1302.4
   5  162.0    1306.5
---------------------
it seems good?

However, I used modified version of LAMMPSrun.py, since REAX parameters 
are stored in units-set called REAL in lammps.

Best regards,
Leon

-- 
Leon Avakyan
Southern Federal University


On 20.01.2018 14:00, ase-users-request at listserv.fysik.dtu.dk wrote:
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>     1. vibration analysis with reaxff (Claudio A. Perottoni)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 19 Jan 2018 10:52:41 -0200
> From: "Claudio A. Perottoni" <caperott at gmail.com>
> To: ase-users at listserv.fysik.dtu.dk
> Subject: [ase-users] vibration analysis with reaxff
> Message-ID:
> 	<CAEHMFWFG-JeKQbFV5SFLnfmYyL2JgHbWC5J09Mc4TFjXeYA6pQ at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi,
>
> I am getting some strange results from vibration analysis of diamond with
> reaxff-lg and reaxffc-2013. I created a diamond structure using
>
> crystal('C', [(0,0,0)], spacegroup=227, cellpar=[a, a, a, 90, 90, 90])
>
> and then converted it to the primitive cell, to speed up calculations and
> facilitate comparison with the expected result (around 1333 cm-1).
> Vibrational analysis was performed as
>
> vib = Vibrations(atoms,delta=0.05)
> vib.run()
> vib.summary()
>
> I have got the following results for different choices of interatomic
> potentials (all calculations performed with LAMMPS):
>
> airebo:
> ---------------------
>    #    meV     cm^-1
> ---------------------
>    0    0.0i      0.0i
>    1    0.0       0.0
>    2    0.0       0.0
>    3  194.9    1571.7
>    4  194.9    1571.7
>    5  194.9    1571.7
> ---------------------
>
> Tersoff:
> ---------------------
>    #    meV     cm^-1
> ---------------------
>    0    0.0i      0.0i
>    1    0.0i      0.0i
>    2    0.0       0.0
>    3  194.6    1569.9
>    4  194.6    1569.9
>    5  194.6    1570.0
> ---------------------
>
> lcbop:
> ---------------------
>    #    meV     cm^-1
> ---------------------
>    0    0.0i      0.0i
>    1    0.0i      0.0i
>    2    0.0       0.0
>    3  146.6    1182.6
>    4  146.6    1182.6
>    5  146.6    1182.6
> ---------------------
>
> reaxff-lg:
> ---------------------
>    #    meV     cm^-1
> ---------------------
>    0    0.0i      0.0i
>    1    0.0i      0.0i
>    2    0.0i      0.0i
>    3  996.3    8035.7
>    4  996.3    8035.7
>    5  996.3    8035.7
> ---------------------
>
> reaxffc-2013:
> ---------------------
>    #    meV     cm^-1
> ---------------------
>    0    0.0i      0.0i
>    1    0.0       0.0
>    2    0.0       0.0
>    3  705.4    5689.8
>    4  705.4    5689.8
>    5  705.4    5689.8
> ---------------------
>
> Has anyone got similar strange results when performing vibrational analysis
> with reaxff/LAMMPS?
>
> Regards,
>
> Claudio
>