[CP2K:5601] Re: Bulk Nickel (and possibly other newbie questions)

[Ralph Koitz]

Hi,

To use spin polarization, you should specify the keyword UKS in the DFT
section and define a MULTIPLICITY.
You may also want to turn on RELAX_MULTIPLICITY in that section.

To use a supercell, you can either manually repeat your coordinates and
load the entire supercell as input coordinates, or specify
MULTIPLE_UNIT_CELL in both the CELL and TOPOLOGY sections of the SUBSYS.
A 6x6x6 supercell should be okay to start out with, but you may want to
check convergence.

We have had decent experience with revPBE as an XC Functional for Ni [1].
BEEFvdW, a more recent addition to cp2k also gives very good bulk nickel,
but it's currently somewhat of a beta-version and you need to compile with
libxc to get it to work.

Best,
Ralph

[1] Gomez-Diaz et al, Theor Chim Acta, 2013

On Fri, Aug 15, 2014 at 2:24 PM, Alex <nedo... at gmail.com> wrote:

> 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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