Re: [Pw_forum] Amorphous Solid

2016-02-24 Thread Alan J. R. Ambrozio
Hi Sarah,

You can do it using Lammps or Quantum Wise. Quantum Wise has this example
using cristobalite. The tutorial is here
http://quantumwise.com/publications/tutorials/item/845-generating-amorphous-structures


You can try the trial license. ;)

cheers
Alan

2016-02-24 18:09 GMT-03:00 Sarah Alpine <sarahalpi...@gmail.com>:

> Thanks for your response, Layla. I don't know about this process; can you
> please direct me to an example or some literature that would describe it in
> detail? Is there QE code anywhere that I can reference?
> Thanks!
>
> On Wed, Feb 24, 2016 at 12:23 PM, Layla Martin-Samos <
> lmartinsa...@gmail.com> wrote:
>
>> Dear Sarah, you can also use a cristobalite supercell and make molecular
>> dynamics at high temperature to obtain a liquid and then quench it.
>>
>> cheers
>>
>> Layla
>>
>> 2016-02-24 20:46 GMT+01:00 Sarah Alpine <sarahalpi...@gmail.com>:
>>
>>> Dear All,
>>>  I am trying to simulate amorphous SiO2. If I am correct, it
>>> structures as tetrahedral arrangements wherein all the tetrahedra are
>>> connected, but have random orientations. So, what I am envisioning to do is
>>> create a supercell of about 20 tetrahedra, and orient these 20 based on a
>>> Monte Carlo method. Is this the correct way to simulate the amorphous SiO2?
>>> And if it is, are there any suggestions for how to use a Monte Carlo method
>>> to find the atomic positions?
>>> I'd appreciate any feed back.
>>> Thanks,
>>> Sarah
>>>
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-- 
Alan J. R. Ambrozio
Visitant PhD student
Room E19-722
Massachusetts Institute of Technology
857 316-8562
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[Pw_forum] Ecutwfc question

2016-01-05 Thread Alan J. R. Ambrozio
I Have a simple question about relaxation. I'm working with a supercell of
216 atoms, an amorphous (carbon + hydrogen) material. The obtained results
for energy were as follows:

Ecut(Ry)   Total EnergyTotal Energy/atom Total force Ry/A
   40  -2350.90316498-10.88381094  0.087283
   60  -2353.20485284-10.89446691  0.076404
   80  -2353.33194348-10.89505529  0.077286
  100  -2353.41150563-10.89542363  0.077982
  120  -2353.42860197-10.89550278  0.078147
  140  -2353.43026886-10.89551050  0.078132
  160  -2353.43072890-10.89551263  0.078139
  180  -2353.43180533-10.89551761  0.078163
  200  -2353.43250424-10.89552085  0.078150


I'd like to perform NMR calculations using GIPAW,  could someone help me,
 what is the best  ecutwf to use (accuracy + computational time)?  I'm
using these pseudopotentials
  C.pbe-tm-gipaw.UPF
  H.pbe-tm-gipaw.UPF

Thank very much.





-- 
Alan J. R. Ambrozio
Visitant PhD student
Room E19-722
Massachusetts Institute of Technology
857 316-8562
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[Pw_forum] Relaxation of hydrogenated amorphous carbon

2015-11-24 Thread Alan J. R. Ambrozio
 0.4627690   0.2887726   0.8059750
 C 0.6948250   0.2688580   0.6407361
 C 0.5695497   0.6308869   0.1567187
 H 0.5563181   0.0535121   0.3011196
 C 0.6278136   0.3956849   0.7478082
 C 0.8790859   0.1586894   0.2806473
 C 0.7279496   0.0937319   0.4025826
 C 0.3933563   0.0161949   0.0995037
 C 0.7415341   0.5272286   0.1943218
 C 0.3494643   0.3359090   0.6588465
 C 0.3811770   0.5461123   0.8407482
 C 0.2257054   0.1875406   0.6617942
 C 0.5477204   0.1963896   0.9447466

CELL_PARAMETERS  {alat}
  0.925200  -0.036749  -0.017857
 -0.036597   0.895520   0.010785
 -0.017919   0.010902   0.966447


K_POINTS automatic
2 2 2  0 0 0

-- 
Alan J. R. Ambrozio
Visitant PhD student
Room E19-722
Massachusetts Institute of Technology
857 316-8562
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