[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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