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[Masayoshi Mikami <mmikami@yk.rim.or.jp>]

Hello,

Although I have little time to try your input now
(at home, midnight ...), I am wondering which kind 
of pseudoptentials were employed in your case. 
(Otherwise, how did you deal with non-linear 
 core-correction for Cr ?)

From the paper (PRB 55 p.10253),
the s, p, d cut-off radii were :
        1.10, 1.00, 1.50 bohr for Cr
        1.25, 1.25, 1.25 bohr for O
Apparently, the Cr pseudopotential should be harder 
than O pseudopotential... 
So, it seems that the shallow core states of Cr 
(3s, 3p) were treated as valence. 
In passing, kindly see also ~ABINIT/Infos/Psp_infos/psp1.data
for caution's sake.

Parenthetically, let me note that I had to take 
such semi-core states of Ti as valence into account
in the calculation of TiO2 (rutile & anatase):
   M.Mikami Jpn.J.App.Phys.39,L847 (2000)
Some other LDA works (cited in the JJAP paper) predicted 
the larger lattice constants than the experimental ones.
(NB: in general, LDA will predict **shorter** lattice 
 constants than experimental ones, by about 1% or so.)
The works that gave the larger lattice constants 
did deal with the shallow-core states as "core" ...

In passing, it would be a good occasion to follow
   http://www.abinit.org/ABINIT/Infos/FAQ.htm#Difference
(and the links therein) as well...

Regards,
Masayoshi
 
From: ilyes.hamdi@fst.rnu.tn
Subject: [abinit-forum] Pressure
Date: Fri, 23 Jan 2004 13:08:12 +0100
Message-ID: <sympa.1074856677.17008.711@abinit.org>

> Dear Abinit users
> I'm trying the optimization of CrO2(semi-metal)in rutile structure, i get 
> problem with convergence of Etot when iscf=5, i change it to 3 and done 
> many convergence study with respect to kpts, ecut and tsmear. Following the 
> paper of Steven P. Lewis et al. Phys rev B55, 10253(1997) the experimental 
> values of a, c and intenal parameter u are 4.419 A, 2.912 A and 0.303 . 
> Optimization after 12 BFGS iteration gives 4.44A, 2.93 A ,0.303 and a 
> pressure of order 10-5 Gpa , and a Magnetisation (Bohr magneton)=  4.01, 
> but when i done a scf calculation with these values, i get a pressure of 
> order 10+2 Gpa and 6.13899687E-09 (Bohr magneton). Any coments would be 
> very helpfull on this difference between the pressures of the two 
> calculations.
> following is my input and a part of the output(SCF calculation).
> ------------------------------------------
> # Crystalline CrO2 : SCF calculation in rutile struc.
> #Definition of the  unit cell
> 
> acell  2*4.44 2.93 angstr        
> rprim  1.0 0.0 0.0    
>        0.0  1.0 0.0   
>        0.0  0.0  1.0
> 
> #Definition of the atom types
> ntypat 2           
> znucl 24 8      
>                            
> 
> #Definition of the atoms
> natom 6           
> typat 1 1 2 2 2 2      
> xred              
>                   
>   0.0 0.0 0.0    
>   1/2 1/2 1/2     
>   0.303 0.303 0   
>   0.697 0.697 0   
>   0.803 0.197 0.5
>   0.197 0.803 0.5
> 
> #Definition of the planewave basis set
> ecut 41       
> 
> 
> #Definition of the k-point grid
> kptopt 1          
> ngkpt 3 3 6                                    
> nshiftk 1         
> shiftk  0.5 0.5 0.5 
>  
> #Definition of the band structure
> nsppol 2
> occopt  3
> nband 24
> tsmear 0.01
> 
> #Definition of the SCF procedure
> nstep 200          
> tolvrs 1.0d-08    
> nline  7    
> iscf   3 
> diemac  1.0d6   
> *****************************************************
> some of output:
> **************************************************
> 
> 
>      iter   Etot(hartree)     deltaE(h) residm    vres2   diffor   maxfor   
> magn
>  ETOT  1  -67.247739840416    -6.72E+01 2.49E-02 9.48E+04 1.4E-01 1.44E-01 
> 0.000
>  ETOT  2  -68.955544632943    -1.71E+00 5.60E-02 1.25E+05 3.7E-01 2.26E-01 
> 0.000
>  ETOT  3  -78.952454147472    -1.00E+01 5.05E-02 3.23E+04 1.4E-01 8.51E-02 
> 0.000
>  ETOT  4  -63.140986093472     1.58E+01 2.45E-01 1.20E+05 2.3E-01 1.44E-01 
> 0.000
>  ETOT  5  -81.869772587910    -1.87E+01 1.60E-01 7.65E+03 2.0E-01 5.49E-02 
> 0.000
>  ETOT  6  -83.076701443028    -1.21E+00 1.20E-01 1.31E+03 3.8E-02 1.70E-02 
> 0.000
>  ETOT  7  -83.222377703227    -1.46E-01 1.14E-02 5.49E+02 1.6E-02 5.37E-04 
> 0.000
>  ETOT  8  -83.309899162123    -8.75E-02 3.97E-03 8.58E+00 4.4E-03 4.96E-03 
> 0.000
>  ETOT  9  -83.311340099561    -1.44E-03 5.47E-04 4.45E-01 4.3E-03 6.56E-04 
> 0.000
>  ETOT 10  -83.311407885475    -6.78E-05 1.07E-03 1.42E-01 7.2E-04 1.38E-03 
> 0.000
>  ETOT 11  -83.311438573177    -3.07E-05 3.88E-03 1.78E-03 3.3E-04 1.05E-03 
> 0.000
>  ETOT 12  -83.311438940661    -3.67E-07 8.88E-04 3.18E-04 6.2E-05 9.87E-04 
> 0.000
>  ETOT 13  -83.311438981139    -4.05E-08 1.76E-03 9.51E-05 2.6E-05 9.61E-04 
> 0.000
>  ETOT 14  -83.311438995664    -1.45E-08 1.41E-03 2.52E-05 4.8E-06 9.66E-04 
> 0.000
>  ETOT 15  -83.311439000529    -4.86E-09 1.92E-03 2.56E-06 7.4E-06 9.58E-04 
> 0.000
>  ETOT 16  -83.311439001698    -1.17E-09 2.40E-03 3.53E-07 1.2E-07 9.59E-04 
> 0.000
>  ETOT 17  -83.311439002418    -7.20E-10 1.13E-03 4.85E-08 7.8E-07 9.58E-04 
> 0.000
>  ETOT 18  -83.311439002934    -5.16E-10 9.01E-04 1.63E-08 1.5E-08 9.58E-04 
> 0.000
>  ETOT 19  -83.311439003245    -3.12E-10 2.73E-04 1.54E-09 1.7E-07 9.58E-04 
> 0.000
> 
>  At SCF step   19       vres2   =  1.54E-09 < tolvrs=  1.00E-08 =>converged.
>     .
>     .
>     .
>     .
> frms,max,avg= 3.2830138E-02 4.9245207E-02   0.000E+00  0.000E+00  0.000E+00 
> e/A
>  length scales=  8.390384034610  8.390384034610  5.536897572389 bohr
>               =  4.440000000000  4.440000000000  2.930000000000 angstroms
>  Fermi energy (hartree) =   0.21252
>  Magnetisation (Bohr magneton)=  6.13899687E-09
>  Total spin up =  1.80000000E+01   Total spin down =  1.80000000E+01
>   .
>   .
>   .
>   .
>   .
>  
>  
> --------------------------------------------------------------------------------
>  Components of total free energy (in Hartree) :
> 
>     Kinetic energy  = 7.84037734506521E+01
>     Hartree energy  = 1.74607103192631E+01
>     XC energy       =-1.84647917827223E+01
>     Ewald energy    =-7.28612822727410E+01
>     PspCore energy  = 3.05749299430425E+00
>     Loc. psp. energy=-7.72168758846552E+01
>     NL   psp  energy=-1.36401206375395E+01
>     >>>>> Internal E=-8.32610938134387E+01
> 
>     -kT*entropy     =-5.03451898067908E-02
>     >>>>>>>>> Etotal=-8.33114390032455E+01
> 
>  Other information on the energy :
>     Total energy(eV)=-2.26701950832303E+03 ; Band energy (Ha)= 
> -1.7300399531E+00
> --------------------------------------------------------------------------------
> 
>  Cartesian components of stress tensor (hartree/bohr^3)
>   sigma(1 1)=  3.55389651E-03  sigma(3 2)=  0.00000000E+00
>   sigma(2 2)=  3.55389651E-03  sigma(3 1)=  0.00000000E+00
>   sigma(3 3)=  4.03266316E-03  sigma(2 1)=  0.00000000E+00
> 
> -Cartesian components of stress tensor (GPa)         [Pressure= -1.0925E+02 
> GPa]
> - sigma(1 1)=  1.04559224E+02  sigma(3 2)=  0.00000000E+00
> - sigma(2 2)=  1.04559224E+02  sigma(3 1)=  0.00000000E+00
> - sigma(3 3)=  1.18645023E+02  sigma(2 1)=  0.00000000E+00
>