Bulk Nickel (and possibly other newbie questions)
Alex
nedo... at gmail.com
Fri Aug 15 21:24:08 UTC 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!
>>
>
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