[CP2K:5601] Re: Bulk Nickel (and possibly other newbie questions)
Ralph Koitz
ralph... at gmail.com
Fri Aug 15 23:36:24 CEST 2014
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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