[Pw_forum] Problem with normal modes of NO gas phase

[Nicola Marzari]

Dear Francesco,


to follow up on Paolo's advice, I would do this:

1) freeze the molecule - i.e. do not relax it.

2) tighten the 2 thresholds a lot -  conv_thr
and tr2_ph (i.e. make them smaller by one order of magnitude, two, etc...).

3) use sssp pseudos: http://materialscloud.org/sssp/

The tables show exactly what is the convergence of the phonons with
cutoff (for molecular solids in the case of N and O),
using the scripts from

http://materialscloud.org/sssp/downloads.html

where you can find all the parameters we used

4) once you feel you are in control on the cutoffs and tolerance 
thresholds, you can start relaxing the molecule. In order to get
very accurate results there, you need to have a very tight criterion on
the relaxation, as well.

				nicola



On 16/11/2017 10:09, Francesco Moriggi wrote:
> Hello, i'm Francesco Moriggi, a master student at the Milan University, 
> i have a problem with ph.x. I am calculating NO frequency and i'm not 
> reaching a convergence in values compared to cutoff energy, using norm 
> conserving and ultrasoft pseudopotentials. Values i get are (i've put an 
> image too in the email):
> 
> *Cutoff   freq Norm    freq US*
> 
> **
> 
> *75        1879.0        1844.4*
> 
> **
> 
> *80        1875.5        1858.2*
> 
> **
> 
> *85        1890.6        1907.1*
> 
> **
> 
> *90        1923.5        1895.2*
> 
> **
> 
> *100      1889.6        1909.3*
> 
> **
> 
> *110      1914.2        1893.1*
> 
> **
> 
> *120      1890.5       1900.4*
> 
> **
> 
> *130       1890.7        1901.0*
> 
> **
> 
> *140        1914.7        1890.9*
> 
> **
> 
> *150        1886.9        ////*
> 
> With Gaussian (aug-cc-pv5Z) i've got *1889.21* cm-1.
> 
> An example of the input of geometry optimization is:
> 
> *&CONTROL**
> **  calculation  = "relax",**
> **  prefix       = "NO",**
> **  pseudo_dir   = 
> "/galileo/home/userexternal/fmoriggi/QE/NO/pseudoNO/ultrasoft",**
> **  outdir       = "./out",**
> **/**
> **&SYSTEM**
> **  ibrav     = 1,**
> **  a         = 20,**
> **  nat       = 2,**
> **  ntyp      = 2,**
> **  nspin     = 2,**
> **  ecutwfc   = 150.D0,**
> **  ecutrho = 1200.D0,**
> **  occupations = 'smearing', smearing = 'gauss', degauss=0.02,**
> **  starting_magnetization(1)=-0.9,**
> **  starting_magnetization(2)=1.5,**
> **/**
> **&ELECTRONS**
> **  electron_maxstep = 500,**
> **  conv_thr    = 1.D-7,**
> **  mixing_beta = 0.7D0,**
> **/**
> **&IONS**
> **/**
> **ATOMIC_SPECIES**
> **O  16.00 O.pbe-van_ak.UPF**
> **N  14.00 N.pbe-van_ak.UPF**
> **ATOMIC_POSITIONS {angstrom}**
> **N  1.16 0.0  0.0**
> **O  0.000  0.0  0.0  0 0 0**
> **K_POINTS**
> **1**
> **0.0 0.0 0.0 1.0*
> 
> Later i've done an scf  with a better conv_thr. This is the input.
> 
> *&CONTROL**
> **  calculation  = "scf",**
> **  prefix       = "150",**
> **  pseudo_dir   = 
> "/galileo/home/userexternal/fmoriggi/QE/NO/pseudoNO/ultrasoft",**
> **  outdir       = "./out150",**
> **/**
> **&SYSTEM**
> **  ibrav     = 1,**
> **  a         = 20,**
> **  nat       = 2,**
> **  ntyp      = 2,**
> **  nspin     = 2,**
> **  ecutwfc   = 150.D0,**
> **  ecutrho   = 1200.D0,**
> **  occupations = 'smearing', smearing = 'gauss', degauss=0.02,**
> **  starting_magnetization(1)=-0.9,**
> **  starting_magnetization(2)=1.5,**
> **/**
> **&ELECTRONS**
> **  electron_maxstep = 500,**
> **  conv_thr    = 1.D-9,**
> **  mixing_beta = 0.7D0,**
> **/**
> **&IONS**
> **/**
> **ATOMIC_SPECIES**
> **O  16.00 O.pbe-van_ak.UPF**
> **N  14.00 N.pbe-van_ak.UPF**
> **ATOMIC_POSITIONS {angstrom}**
> **N  1.166278 0.0  0.0**
> **O  0.000  0.0  0.0  0 0 0**
> **K_POINTS**
> **1**
> **0.0 0.0 0.0 1.0*
> 
> And then i run the ph.x with this input:
> 
> *phonon calculation - NO**
> ** &inputph**
> **  tr2_ph=4.0d-12,**
> **  prefix='150'**
> **  amass(1)=14.007,**
> **  amass(2)=15.9994,**
> **  outdir='/galileo/home/userexternal/fmoriggi/QE/NO/relax/ultra/out150'**
> ** /**
> ** 0.0 0.0 0.0*
> 
> If you can help me it would be very useful to my future TiO2 based 
> calculations.
> 
> 
> Best regards,
> 
> Francesco Moriggi
> 
> Webpage: http://users.unimi.it/ceotto/about_FrancescoMoriggi.html
> 
> 
> 
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-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project