Bulk Nickel (and possibly other newbie questions)

Alex nedo... at gmail.com
Fri Aug 15 23:24:08 CEST 2014


Also, I just redid the calculation with 

    BASIS_SET DZV-GTH-PADE-q18
   POTENTIAL GTH-PADE-q18

Same energy within I believe five decimal places. As far as the correct 
choice of the XC-potential-basis combination, what would be better in my 
case? As I've said before, I am really new to this... Any reference to that 
effect would be great.

Thank you.

On Friday, August 15, 2014 3:05:37 PM UTC-6, Marcella Iannuzzi wrote:
>
> Hi
>
> Just few remarks.
>
> For the fcc bulk Ni energy, you need to construct a supercell, since there 
> is no k-point sampling,
> and check the convergence of the result with system size.
>
> PADE is probably not an optimal choice for the XC functional, anyway, you 
> should use consistent potential and basis set,
> i.e. for the same number of valence electrons (in your input, the PP is 
> for 10 v.e. and the BS for 18)
>
> If you don't specify in in the input, no spin polarisation is considered.
>
> Regards
>
> Marcella
>   
>
> On Friday, August 15, 2014 10:19:59 PM UTC+2, Alex wrote:
>>
>> Hi all,
>>
>> I am very new to DFT calculations, let alone CP2k, so some level of 
>> idiocy on my part should be expected.
>> As a simple test, I am trying to calculate the binding energy of a Ni 
>> atom in a bulk crystal. The relevant portion of the input shown below:
>>
>> ***
>> &GLOBAL
>>   PROJECT Ni_inp_test
>>   RUN_TYPE ENERGY_FORCE
>>   PRINT_LEVEL LOW
>> &END GLOBAL
>> &FORCE_EVAL
>>   METHOD Quickstep
>>   &SUBSYS
>>     &KIND Ni
>>       ELEMENT Ni
>>       BASIS_SET DZV-GTH-PADE-q18
>>       POTENTIAL GTH-PADE-q10
>>     &END KIND
>>     &CELL
>>       A     1.765000    1.765000    0.000000
>>       B     0.000000    1.765000    1.765000
>>       C    1.765000    0.000000    1.765000
>>       PERIODIC XYZ
>>     &END CELL
>>     &COORD
>>       Ni    0.000000000    0.000000000    0.000000000
>>     &END COORD
>>   &END SUBSYS
>>   &DFT
>>     BASIS_SET_FILE_NAME  BASIS_SET
>>     POTENTIAL_FILE_NAME  GTH_POTENTIALS
>>     &QS
>>       EPS_DEFAULT 1.0E-10
>>     &END QS
>>     &MGRID
>>       NGRIDS 4
>>       CUTOFF 300
>>       REL_CUTOFF 60
>>     &END MGRID
>>     &XC
>>       &XC_FUNCTIONAL PADE
>>       &END XC_FUNCTIONAL
>>     &END XC
>>     &SCF
>>       SCF_GUESS ATOMIC
>>       EPS_SCF 1.0E-7
>>       MAX_SCF 300
>>       ADDED_MOS 10
>>       &DIAGONALIZATION  ON
>>         ALGORITHM STANDARD
>>       &END DIAGONALIZATION
>>       &MIXING  T
>>         METHOD BROYDEN_MIXING
>>         ALPHA 0.4
>>         NBROYDEN 8
>>       &END MIXING
>>       &SMEAR ON
>>         METHOD FERMI_DIRAC
>>         ELECTRONIC_TEMPERATURE [K] 300
>>       &END SMEAR
>>     &END SCF
>>   &END DFT
>>   &PRINT
>>     &FORCES ON
>>     &END FORCES
>>   &END PRINT
>> &END FORCE_EVAL
>>
>> ***
>>
>> This yields a total energy of E1=-35.155 a.u. after convergence.
>>
>> Then I decided to calculate the "vacuum" energy of an isolated atom, 
>> input below:
>>
>> &GLOBAL
>>   PROJECT Ni_inp_test
>>   RUN_TYPE ENERGY_FORCE
>>   PRINT_LEVEL LOW
>> &END GLOBAL
>> &FORCE_EVAL
>>   METHOD Quickstep
>>   &SUBSYS
>>     &KIND Ni
>>       ELEMENT Ni
>>       BASIS_SET DZV-GTH-PADE-q18
>>       POTENTIAL GTH-PADE-q10
>>     &END KIND
>>     &CELL
>>       A     30.00000    0.000000    0.000000
>>       B     0.000000    30.00000    0.000000
>>       C    0.000000    0.000000    30.00000
>>     &END CELL
>>     &COORD
>>       Ni    0.000000000    0.000000000    0.000000000
>>     &END COORD
>>   &END SUBSYS
>>   &DFT
>>     BASIS_SET_FILE_NAME  BASIS_SET
>>     POTENTIAL_FILE_NAME  GTH_POTENTIALS
>>     &QS
>>       EPS_DEFAULT 1.0E-10
>>     &END QS
>>     &MGRID
>>       NGRIDS 4
>>       CUTOFF 300
>>       REL_CUTOFF 60
>>     &END MGRID
>>     &XC
>>       &XC_FUNCTIONAL PADE
>>       &END XC_FUNCTIONAL
>>     &END XC
>>     &SCF
>>       SCF_GUESS ATOMIC
>>       EPS_SCF 1.0E-7
>>       MAX_SCF 300
>>       ADDED_MOS 10
>>       &DIAGONALIZATION  ON
>>         ALGORITHM STANDARD
>>       &END DIAGONALIZATION
>>       &MIXING  T
>>         METHOD BROYDEN_MIXING
>>         ALPHA 0.4
>>         NBROYDEN 8
>>       &END MIXING
>>       &SMEAR ON
>>         METHOD FERMI_DIRAC
>>         ELECTRONIC_TEMPERATURE [K] 300
>>       &END SMEAR
>>     &END SCF
>>   &END DFT
>>   &PRINT
>>     &FORCES ON
>>     &END FORCES
>>   &END PRINT
>> &END FORCE_EVAL
>>
>> ***
>>
>> This also converges and yields a total energy E2=-34.555 a.u.
>>
>>
>> Hence, my questions:
>>
>> 1. Is this even the correct way of calculating what I want, including the 
>> energy calculations, XC functional, and basis?
>> 2. Should the spin properties be explicitly set in the input? There are 
>> none now.
>> 3. Am I setting up the FCC lattice correctly (first input file)? My 
>> translation vectors are set by the ABC values, but I have no idea whether 
>> this is right.
>> 4. If the first simulation yields the total energy of the system and the 
>> FCC lattice implies 12 nearest neighbors, then removing the center would 
>> change the total energy by (E1-E2)/6, which isn't the experimental -4.4 eV. 
>> Am I completely off track here? :)
>>
>> Thanks a lot!
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20140815/e0db4857/attachment.html>


More information about the CP2K-user mailing list