Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-05 Thread Christoph Wolf 
Dear colleagues,

Thank you all very much for your input which was a great help. With regard
to the last hint (distortion of the octahedral configuration and HSE) I
wanted to ask if there is a "correct" strategy to find the (Jahn Teller)
distorted configuration.

I tried to replace the Fe iron for example in x and y direction preserving
z coordinate and relax the system to 1e-6 a.u. residual forces but the
system always "pops back" into the original configuration with the Fermi
level inside the band.

Thanks again to everyone and with best regards,

Chris

-- 
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Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-05 Thread Christoph Wolf 
Dear colleagues,

Thank you all very much for your input which was a great help. With regard
to the last hint (distortion of the octahedral configuration and HSE) I
wanted to ask if there is a "correct" strategy to find the (Jahn Teller)
distorted configuration.

I tried to replace the Fe iron for example in x and y direction preserving
z coordinate and relax the system to 1e-6 a.u. residual forces but the
system always "pops back" into the original configuration with the Fermi
level inside the band.

Thanks again to everyone and with best regards,

Chris

-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-04 Thread José C . Conesa 

Hi,

GGA is certainly inadequate to sytudy this system. My recommendation 
would be to carry out a hybrid functional calculation, e.g. with HSE. 
This cell has not too may atoms, it should be feasible. Use at least a 
4x4x4 Brillouin zone sampling. Displacing Fe from the symmetry position 
is of course necessary, then the structure should be relaxed. And a 
spin-polarized calculation will be necessary as well. I find likely that 
the system will have in the end a low spin configuration, with all 
Fe(3d) electrons filling the t(2g) manifold which would be well 
separated from the e(g) manifold, therefore having a clear nonmetallic 
behaviour.


Good luck,

JC Conesa


El 04/03/2018 a las 9:51, Pietro Delugas escribió:
If the band is flat or almost flat maybe one could try to use LDA+U, ( 
or some hybrid functional with exact exchange if the cell size is  
feasible ) displace Fe a little if it is in a  too symmetric position, 
relax and see if it is possible to split Fe impurity levels. If so one 
can  compute Fe Born Charges by finite differences.



Il 04 mar 2018 9:27 AM, Paolo Giannozzi  ha 
scritto:


The problem is that the true system is not metallic, but in a band
picture it is, even for a supercell of 1m side. Maybe one might
compute phonons as for a metal, then use dielectirc constant and
effective charges of the insulating host crystal. Not sure what
one can use for the effective charges of Fe, though.

Paolo

On Sun, Mar 4, 2018 at 8:39 AM, Pietro Delugas > wrote:

Hello Chris

If the system is metallic, no matter how bad a conductor it
can be, in a finite time it will be able to screen any
constant electric field. This  is as to say that the static
dielectric constant is infinite.

Regards Pietro


Il 04 mar 2018 8:03 AM, Christoph Wolf
 ha scritto:

Dear all,

I have a fairly general question and I hope I can pick
someone's brain:

If an insulator or semiconductor is doped with a metal
narrow bands determined by the crystal field emerge and
often the fermi level lies within one of the bands, i.e.
the "bands cut the fermi level", which is often called a
characteristic of a conductor but in the bigger picture no
electrons would be able to cross from the VB to the CB,
i.e. the host system is an insulator.

When attempting to calculate the phonons of a Mg7O8Fe
supercell the  dieletric constant (in the case of pure MgO
eps~3.1) cannot be computed

     Electric Fields Calculation
     ik   1 ibnd   0 linter: root not converged 2.635E-07

..

     End of electric fields calculation

          Dielectric constant in cartesian axis

(**  0.000244141      -0.001708984 )
          ( -0.000244141**      0.000244141 )
          ( -0.000732422  0.000732422** )

And I am wondering if that system should be treated as a
metal instead (epsil    = .false.,) during the phonon run?

--

  prefix   = 'MgO',
  epsil    = .true.,
  alpha_mix(1) =0.4
  alpha_mix(2) =0.4
  fildyn   = 'MgO.dyn',
  ldisp    = .true.
  fildvscf = 'dvscf'
  amass(1) = 24.30500
  amass(2) = 15.99900
  amass(3) = 55.84500
  outdir='./',
  nq1=6,
  nq2=6,
  nq3=6,
  tr2_ph   =  1.0d-12,
 /

Any hint is welcome!

Thanks in advance for your help and a nice Sunday everyone!

Chris
-- 
Postdoctoral Researcher

Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea



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Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222




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Instituto de Catálisis y Petroleoquímica, CSIC
Marie Curie 2, Cantoblanco
28049 Madrid, Spain
Tel. (+34)915854766



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Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-04 Thread José C . Conesa 

Hi,

GGA is certainly inadequate to sytudy this system. My recommendation 
would be to carry out a hybrid functional calculation, e.g. with HSE. 
This cell has not too may atoms, it should be feasible. Use at least a 
4x4x4 Brillouin zone sampling. Displacing Fe from the symmetry position 
is of course necessary, then the structure should be relaxed. And a 
spin-polarized calculation will be necessary as well. I find likely that 
the system will have in the end a low spin configuration, with all 
Fe(3d) electrons filling the t(2g) manifold which would be well 
separated from the e(g) manifold, therefore having a clear nonmetallic 
behaviour.


Good luck,

JC Conesa


El 04/03/2018 a las 9:51, Pietro Delugas escribió:
If the band is flat or almost flat maybe one could try to use LDA+U, ( 
or some hybrid functional with exact exchange if the cell size is  
feasible ) displace Fe a little if it is in a  too symmetric position, 
relax and see if it is possible to split Fe impurity levels. If so one 
can  compute Fe Born Charges by finite differences.



Il 04 mar 2018 9:27 AM, Paolo Giannozzi  ha 
scritto:


The problem is that the true system is not metallic, but in a band
picture it is, even for a supercell of 1m side. Maybe one might
compute phonons as for a metal, then use dielectirc constant and
effective charges of the insulating host crystal. Not sure what
one can use for the effective charges of Fe, though.

Paolo

On Sun, Mar 4, 2018 at 8:39 AM, Pietro Delugas > wrote:

Hello Chris

If the system is metallic, no matter how bad a conductor it
can be, in a finite time it will be able to screen any
constant electric field. This  is as to say that the static
dielectric constant is infinite.

Regards Pietro


Il 04 mar 2018 8:03 AM, Christoph Wolf
 ha scritto:

Dear all,

I have a fairly general question and I hope I can pick
someone's brain:

If an insulator or semiconductor is doped with a metal
narrow bands determined by the crystal field emerge and
often the fermi level lies within one of the bands, i.e.
the "bands cut the fermi level", which is often called a
characteristic of a conductor but in the bigger picture no
electrons would be able to cross from the VB to the CB,
i.e. the host system is an insulator.

When attempting to calculate the phonons of a Mg7O8Fe
supercell the  dieletric constant (in the case of pure MgO
eps~3.1) cannot be computed

     Electric Fields Calculation
     ik   1 ibnd   0 linter: root not converged 2.635E-07

..

     End of electric fields calculation

          Dielectric constant in cartesian axis

(**  0.000244141      -0.001708984 )
          ( -0.000244141**      0.000244141 )
          ( -0.000732422  0.000732422** )

And I am wondering if that system should be treated as a
metal instead (epsil    = .false.,) during the phonon run?

--

  prefix   = 'MgO',
  epsil    = .true.,
  alpha_mix(1) =0.4
  alpha_mix(2) =0.4
  fildyn   = 'MgO.dyn',
  ldisp    = .true.
  fildvscf = 'dvscf'
  amass(1) = 24.30500
  amass(2) = 15.99900
  amass(3) = 55.84500
  outdir='./',
  nq1=6,
  nq2=6,
  nq3=6,
  tr2_ph   =  1.0d-12,
 /

Any hint is welcome!

Thanks in advance for your help and a nice Sunday everyone!

Chris
-- 
Postdoctoral Researcher

Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea



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Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222




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Instituto de Catálisis y Petroleoquímica, CSIC
Marie Curie 2, Cantoblanco
28049 Madrid, Spain
Tel. (+34)915854766



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Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-04 Thread Pietro Delugas 
If the band is flat or almost flat maybe one could try to use LDA+U, ( or some hybrid functional with exact exchange if the cell size is  feasible ) displace Fe a little if it is in a  too symmetric position, relax and see if it is possible to split Fe impurity levels. If so one can  compute Fe Born Charges by finite differences. Il 04 mar 2018 9:27 AM, Paolo Giannozzi  ha scritto:The problem is that the true system is not metallic, but in a band picture it is, even for a supercell of 1m side. Maybe one might compute phonons as for a metal, then use dielectirc constant and effective charges of the insulating host crystal. Not sure what one can use for the effective charges of Fe, though.PaoloOn Sun, Mar 4, 2018 at 8:39 AM, Pietro Delugas  wrote:Hello ChrisIf the system is metallic, no matter how bad a conductor it can be, in a finite time it will be able to screen any constant electric field. This  is as to say that the static dielectric constant is infinite. Regards PietroIl 04 mar 2018 8:03 AM, Christoph Wolf  ha scritto:Dear all,I have a fairly general question and I hope I can pick someone's brain:If an insulator or semiconductor is doped with a metal narrow bands determined by the crystal field emerge and often the fermi level lies within one of the bands, i.e. the "bands cut the fermi level", which is often called a characteristic of a conductor but in the bigger picture no electrons would be able to cross from the VB to the CB, i.e. the host system is an insulator.When attempting to calculate the phonons of a Mg7O8Fe supercell the  dieletric constant (in the case of pure MgO eps~3.1) cannot be computed     Electric Fields Calculation     ik   1 ibnd   0 linter: root not converged  2.635E-07..     End of electric fields calculation          Dielectric constant in cartesian axis           (**       0.000244141      -0.001708984 )          (      -0.000244141**       0.000244141 )          (      -0.000732422       0.000732422** )And I am wondering if that system should be treated as a metal instead (epsil    = .false.,) during the phonon run?--  prefix   = 'MgO',  epsil    = .true.,  alpha_mix(1) =0.4  alpha_mix(2) =0.4  fildyn   = 'MgO.dyn',  ldisp    = .true.  fildvscf = 'dvscf'  amass(1) = 24.30500  amass(2) = 15.99900  amass(3) = 55.84500  outdir='./',  nq1=6,  nq2=6,  nq3=6,  tr2_ph   =  1.0d-12, /Any hint is welcome!Thanks in advance for your help and a nice Sunday everyone!Chris -- Postdoctoral ResearcherCenter for Quantum Nanoscience, Institute for Basic ScienceEwha Womans University, Seoul, South Korea

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Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-04 Thread Pietro Delugas 
If the band is flat or almost flat maybe one could try to use LDA+U, ( or some hybrid functional with exact exchange if the cell size is  feasible ) displace Fe a little if it is in a  too symmetric position, relax and see if it is possible to split Fe impurity levels. If so one can  compute Fe Born Charges by finite differences. Il 04 mar 2018 9:27 AM, Paolo Giannozzi  ha scritto:The problem is that the true system is not metallic, but in a band picture it is, even for a supercell of 1m side. Maybe one might compute phonons as for a metal, then use dielectirc constant and effective charges of the insulating host crystal. Not sure what one can use for the effective charges of Fe, though.PaoloOn Sun, Mar 4, 2018 at 8:39 AM, Pietro Delugas  wrote:Hello ChrisIf the system is metallic, no matter how bad a conductor it can be, in a finite time it will be able to screen any constant electric field. This  is as to say that the static dielectric constant is infinite. Regards PietroIl 04 mar 2018 8:03 AM, Christoph Wolf  ha scritto:Dear all,I have a fairly general question and I hope I can pick someone's brain:If an insulator or semiconductor is doped with a metal narrow bands determined by the crystal field emerge and often the fermi level lies within one of the bands, i.e. the "bands cut the fermi level", which is often called a characteristic of a conductor but in the bigger picture no electrons would be able to cross from the VB to the CB, i.e. the host system is an insulator.When attempting to calculate the phonons of a Mg7O8Fe supercell the  dieletric constant (in the case of pure MgO eps~3.1) cannot be computed     Electric Fields Calculation     ik   1 ibnd   0 linter: root not converged  2.635E-07..     End of electric fields calculation          Dielectric constant in cartesian axis           (**       0.000244141      -0.001708984 )          (      -0.000244141**       0.000244141 )          (      -0.000732422       0.000732422** )And I am wondering if that system should be treated as a metal instead (epsil    = .false.,) during the phonon run?--  prefix   = 'MgO',  epsil    = .true.,  alpha_mix(1) =0.4  alpha_mix(2) =0.4  fildyn   = 'MgO.dyn',  ldisp    = .true.  fildvscf = 'dvscf'  amass(1) = 24.30500  amass(2) = 15.99900  amass(3) = 55.84500  outdir='./',  nq1=6,  nq2=6,  nq3=6,  tr2_ph   =  1.0d-12, /Any hint is welcome!Thanks in advance for your help and a nice Sunday everyone!Chris -- Postdoctoral ResearcherCenter for Quantum Nanoscience, Institute for Basic ScienceEwha Womans University, Seoul, South Korea

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Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-04 Thread Paolo Giannozzi 
The problem is that the true system is not metallic, but in a band picture
it is, even for a supercell of 1m side. Maybe one might compute phonons as
for a metal, then use dielectirc constant and effective charges of the
insulating host crystal. Not sure what one can use for the effective
charges of Fe, though.

Paolo

On Sun, Mar 4, 2018 at 8:39 AM, Pietro Delugas  wrote:

> Hello Chris
>
> If the system is metallic, no matter how bad a conductor it can be, in a
> finite time it will be able to screen any constant electric field. This  is
> as to say that the static dielectric constant is infinite.
>
> Regards Pietro
>
>
> Il 04 mar 2018 8:03 AM, Christoph Wolf  ha
> scritto:
>
> Dear all,
>
> I have a fairly general question and I hope I can pick someone's brain:
>
> If an insulator or semiconductor is doped with a metal narrow bands
> determined by the crystal field emerge and often the fermi level lies
> within one of the bands, i.e. the "bands cut the fermi level", which is
> often called a characteristic of a conductor but in the bigger picture no
> electrons would be able to cross from the VB to the CB, i.e. the host
> system is an insulator.
>
> When attempting to calculate the phonons of a Mg7O8Fe supercell the
> dieletric constant (in the case of pure MgO eps~3.1) cannot be computed
>
>  Electric Fields Calculation
>  ik   1 ibnd   0 linter: root not converged  2.635E-07
> 
> ..
>
>  End of electric fields calculation
>
>   Dielectric constant in cartesian axis
>
>   (**   0.000244141  -0.001708984 )
>   (  -0.000244141**   0.000244141 )
>   (  -0.000732422   0.000732422** )
>
> And I am wondering if that system should be treated as a metal instead
> (epsil= .false.,) during the phonon run?
>
> --
> 
>   prefix   = 'MgO',
>   epsil= .true.,
>   alpha_mix(1) =0.4
>   alpha_mix(2) =0.4
>   fildyn   = 'MgO.dyn',
>   ldisp= .true.
>   fildvscf = 'dvscf'
>   amass(1) = 24.30500
>   amass(2) = 15.99900
>   amass(3) = 55.84500
>   outdir='./',
>   nq1=6,
>   nq2=6,
>   nq3=6,
>   tr2_ph   =  1.0d-12,
>  /
>
> Any hint is welcome!
>
> Thanks in advance for your help and a nice Sunday everyone!
>
> Chris
> --
> Postdoctoral Researcher
> Center for Quantum Nanoscience, Institute for Basic Science
> Ewha Womans University, Seoul, South Korea
>
>
>
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Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-03 Thread Pietro Delugas 
Hello ChrisIf the system is metallic, no matter how bad a conductor it can be, in a finite time it will be able to screen any constant electric field. This  is as to say that the static dielectric constant is infinite. Regards PietroIl 04 mar 2018 8:03 AM, Christoph Wolf  ha scritto:Dear all,I have a fairly general question and I hope I can pick someone's brain:If an insulator or semiconductor is doped with a metal narrow bands determined by the crystal field emerge and often the fermi level lies within one of the bands, i.e. the "bands cut the fermi level", which is often called a characteristic of a conductor but in the bigger picture no electrons would be able to cross from the VB to the CB, i.e. the host system is an insulator.When attempting to calculate the phonons of a Mg7O8Fe supercell the  dieletric constant (in the case of pure MgO eps~3.1) cannot be computed     Electric Fields Calculation     ik   1 ibnd   0 linter: root not converged  2.635E-07..     End of electric fields calculation          Dielectric constant in cartesian axis           (**       0.000244141      -0.001708984 )          (      -0.000244141**       0.000244141 )          (      -0.000732422       0.000732422** )And I am wondering if that system should be treated as a metal instead (epsil    = .false.,) during the phonon run?--  prefix   = 'MgO',  epsil    = .true.,  alpha_mix(1) =0.4  alpha_mix(2) =0.4  fildyn   = 'MgO.dyn',  ldisp    = .true.  fildvscf = 'dvscf'  amass(1) = 24.30500  amass(2) = 15.99900  amass(3) = 55.84500  outdir='./',  nq1=6,  nq2=6,  nq3=6,  tr2_ph   =  1.0d-12, /Any hint is welcome!Thanks in advance for your help and a nice Sunday everyone!Chris -- Postdoctoral ResearcherCenter for Quantum Nanoscience, Institute for Basic ScienceEwha Womans University, Seoul, South Korea

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Re: [QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-03 Thread Pietro Delugas 
Hello ChrisIf the system is metallic, no matter how bad a conductor it can be, in a finite time it will be able to screen any constant electric field. This  is as to say that the static dielectric constant is infinite. Regards PietroIl 04 mar 2018 8:03 AM, Christoph Wolf  ha scritto:Dear all,I have a fairly general question and I hope I can pick someone's brain:If an insulator or semiconductor is doped with a metal narrow bands determined by the crystal field emerge and often the fermi level lies within one of the bands, i.e. the "bands cut the fermi level", which is often called a characteristic of a conductor but in the bigger picture no electrons would be able to cross from the VB to the CB, i.e. the host system is an insulator.When attempting to calculate the phonons of a Mg7O8Fe supercell the  dieletric constant (in the case of pure MgO eps~3.1) cannot be computed     Electric Fields Calculation     ik   1 ibnd   0 linter: root not converged  2.635E-07..     End of electric fields calculation          Dielectric constant in cartesian axis           (**       0.000244141      -0.001708984 )          (      -0.000244141**       0.000244141 )          (      -0.000732422       0.000732422** )And I am wondering if that system should be treated as a metal instead (epsil    = .false.,) during the phonon run?--  prefix   = 'MgO',  epsil    = .true.,  alpha_mix(1) =0.4  alpha_mix(2) =0.4  fildyn   = 'MgO.dyn',  ldisp    = .true.  fildvscf = 'dvscf'  amass(1) = 24.30500  amass(2) = 15.99900  amass(3) = 55.84500  outdir='./',  nq1=6,  nq2=6,  nq3=6,  tr2_ph   =  1.0d-12, /Any hint is welcome!Thanks in advance for your help and a nice Sunday everyone!Chris -- Postdoctoral ResearcherCenter for Quantum Nanoscience, Institute for Basic ScienceEwha Womans University, Seoul, South Korea

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[QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-03 Thread Christoph Wolf 
Dear all,

I have a fairly general question and I hope I can pick someone's brain:

If an insulator or semiconductor is doped with a metal narrow bands
determined by the crystal field emerge and often the fermi level lies
within one of the bands, i.e. the "bands cut the fermi level", which is
often called a characteristic of a conductor but in the bigger picture no
electrons would be able to cross from the VB to the CB, i.e. the host
system is an insulator.

When attempting to calculate the phonons of a Mg7O8Fe supercell the
dieletric constant (in the case of pure MgO eps~3.1) cannot be computed

 Electric Fields Calculation
 ik   1 ibnd   0 linter: root not converged  2.635E-07

..

 End of electric fields calculation

  Dielectric constant in cartesian axis

  (**   0.000244141  -0.001708984 )
  (  -0.000244141**   0.000244141 )
  (  -0.000732422   0.000732422** )

And I am wondering if that system should be treated as a metal instead
(epsil= .false.,) during the phonon run?

--

  prefix   = 'MgO',
  epsil= .true.,
  alpha_mix(1) =0.4
  alpha_mix(2) =0.4
  fildyn   = 'MgO.dyn',
  ldisp= .true.
  fildvscf = 'dvscf'
  amass(1) = 24.30500
  amass(2) = 15.99900
  amass(3) = 55.84500
  outdir='./',
  nq1=6,
  nq2=6,
  nq3=6,
  tr2_ph   =  1.0d-12,
 /

Any hint is welcome!

Thanks in advance for your help and a nice Sunday everyone!

Chris
-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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[QE-users] Metal-substituted semiconductor: treat as metal or insulator for phonons

2018-03-03 Thread Christoph Wolf 
Dear all,

I have a fairly general question and I hope I can pick someone's brain:

If an insulator or semiconductor is doped with a metal narrow bands
determined by the crystal field emerge and often the fermi level lies
within one of the bands, i.e. the "bands cut the fermi level", which is
often called a characteristic of a conductor but in the bigger picture no
electrons would be able to cross from the VB to the CB, i.e. the host
system is an insulator.

When attempting to calculate the phonons of a Mg7O8Fe supercell the
dieletric constant (in the case of pure MgO eps~3.1) cannot be computed

 Electric Fields Calculation
 ik   1 ibnd   0 linter: root not converged  2.635E-07

..

 End of electric fields calculation

  Dielectric constant in cartesian axis

  (**   0.000244141  -0.001708984 )
  (  -0.000244141**   0.000244141 )
  (  -0.000732422   0.000732422** )

And I am wondering if that system should be treated as a metal instead
(epsil= .false.,) during the phonon run?

--

  prefix   = 'MgO',
  epsil= .true.,
  alpha_mix(1) =0.4
  alpha_mix(2) =0.4
  fildyn   = 'MgO.dyn',
  ldisp= .true.
  fildvscf = 'dvscf'
  amass(1) = 24.30500
  amass(2) = 15.99900
  amass(3) = 55.84500
  outdir='./',
  nq1=6,
  nq2=6,
  nq3=6,
  tr2_ph   =  1.0d-12,
 /

Any hint is welcome!

Thanks in advance for your help and a nice Sunday everyone!

Chris
-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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