[CP2K:5601] Re: Bulk Nickel (and possibly other newbie questions)
Alex
nedo... at gmail.com
Sat Aug 16 00:14:05 CEST 2014
Hi Ralph,
This is all very useful, thanks a bunch. I added cell multiplicity
explicitly, as you suggested.
Since I am not the owner of the installation (I'm running it on a remote
cluster), I won't be able to compile anything myself, so I'll stick with
what's there now (I think we have Debian binaries). I am looking at the
reference you provided... For PBE/revPBE XC, what potential and basis did
you use, exactly (assuming they are part of the package)? Also, did you use
s=1/2 for the multiplicity in this case, i.e. the MULTIPLICITY param would
be 2?..
Thank you,
Alex
On Friday, August 15, 2014 3:36:47 PM UTC-6, Ralph wrote:
>
> 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 <ned... at gmail.com <javascript:>>
> 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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>
>
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