[CP2K-user] Reproducing Born-Haber cycle energies for teaching purposes

[Matt W]

Hi Henrique,

there are several issues with your calculation. I'll try and put up a full 
how-to on this as it addresses several useful points:

(i) calculating Na+ accurately requires using non-periodic boundary 
conditions. Set periodic none in &CELL and &POISSON section, along with 
PSOLVER wavelet
(ii) you need a larger unit cell to accurately represent NaCl using gamma 
point only - I used MULTIPLE_UNIT_CELL 4 4 4 (you could use k-points 
instead)
(iii) you need a _much_ larger cutoff for Na - 1500 Ry is still not 
adequate for fully converged stress tensor(!)

To avoid the non cubic optimization you saw, you need to explicitly set 
SYMMETRY CUBIC in the &CELL section. CP2K doesn't find the symmetry by 
itself so doesn't keep it.

With these changes I got an enthalpy of ~-990 kJ/mol which is within ~12% 
of the value you quote with a difference of only ~10 kJ/mol between DZVP 
and TZV2P basis, so I guess this is likely close to the PBE value. This is 
a zero K value, not sure about the experimental data. 

HTH,

Matt

On Sunday, January 6, 2019 at 4:22:52 PM UTC, Henrique Junior wrote:
>
> Dear colleagues,
>
> For teaching purposes I’m trying to reproduce Born-Haber Cycle energies 
> using CP2K (6.1). Since this is just for didactic purposes, the simplest 
> cases, like NaCl, KBr etc are more than enough, but here is what I’ve got 
> so far:
>
>
> * Starting from .cif files for the solid parts (available online) I have 
> user GEO and CELL Opt to get an optimized energy:
>
> &GLOBAL
>
> PROJECT NaCl
>
> RUN_TYPE CELL_OPT
>
> PRINT_LEVEL LOW
>
> &END GLOBAL
>
>
> &MOTION
>
> &CELL_OPT
>
> KEEP_ANGLES true
>
> KEEP_SYMMETRY true
>
> MAX_ITER 2000
>
> OPTIMIZER BFGS
>
> TYPE DIRECT_CELL_OPT
>
> EXTERNAL_PRESSURE 10000.0 0.0 0.0 0.0 10000.0 0.0 0.0 0.0 10000.0
>
> PRESSURE_TOLERANCE 10000
>
> &END CELL_OPT
>
> &GEO_OPT
>
> OPTIMIZER BFGS
>
> &END GEO_OPT
>
> &END MOTION
>
>
> * For the gaseous parts I have performed only GEO_OPT in a large (fixed) 
> unitary cell.
>
>
> *It is interesting to note that despite using KEEP_ANGLES true and 
> KEEP_SYMMETRY true the final cell is not perfectly cubic (why?).*
>
>
> Testing for the energy of part of the cycle (NaCl energy is divided by 4, 
> and Cl2 is divided by 2): 
>
>
> Na+(g) + ½ Cl2(g) → NaCl(s)
>
> (-47.3764756753857 + -14.9639608215114) → -62.3002586417268
>
> Results in -0.04017785517032 Eh or -105.48693988 KJ/mol
>
>
> An energy that is not even close to what is expected (The entire 
> born-haber cycle is attached).
>
>
> So, here is the question: What am I doing wrong? Can the Born-haber cycle 
> energies be obtained using CP2k (maybe with a different approach?)?
>
> Thanks in advance for any help
>
>
>
>
> Here is the complete input:
>
> &GLOBAL
>
> PROJECT NaCl
>
> RUN_TYPE CELL_OPT
>
> PRINT_LEVEL LOW
>
> &END GLOBAL
>
>
> &MOTION
>
> &CELL_OPT
>
> KEEP_ANGLES true
>
> KEEP_SYMMETRY true
>
> MAX_ITER 20000
>
> OPTIMIZER BFGS
>
> TYPE DIRECT_CELL_OPT
>
> EXTERNAL_PRESSURE 10000.0 0.0 0.0 0.0 10000.0 0.0 0.0 0.0 10000.0
>
> PRESSURE_TOLERANCE 10000
>
> &END CELL_OPT
>
> &GEO_OPT
>
> OPTIMIZER BFGS
>
> &END GEO_OPT
>
> &END MOTION
>
>
> &FORCE_EVAL
>
> STRESS_TENSOR DIAGONAL_ANALYTICAL
>
> METHOD QS
>
>
> &DFT
>
>
> &QS
>
> EPS_DEFAULT 1.0E-12
>
> EXTRAPOLATION ASPC
>
> EXTRAPOLATION_ORDER 3
>
> METHOD GPW
>
> PW_GRID NS-FULLSPACE
>
> MAP_CONSISTENT
>
> &END QS
>
>
> CHARGE 0
>
> MULTIPLICITY 1
>
> BASIS_SET_FILE_NAME BASIS
>
> POTENTIAL_FILE_NAME POTENTIAL
>
>
> &MGRID
>
> COMMENSURATE
>
> CUTOFF 600
>
> NGRIDS 5
>
> REALSPACE
>
> RELATIVE_CUTOFF 80
>
> &RS_GRID
>
> DISTRIBUTION_TYPE AUTOMATIC
>
> &END RS_GRID
>
> &END MGRID
>
>
> &XC
>
> &XC_FUNCTIONAL PBE
>
> &END XC_FUNCTIONAL
>
> &END XC
>
> &SCF
>
> EPS_SCF 1.0E-7
>
> MAX_DIIS 4
>
> MAX_SCF 50000
>
> SCF_GUESS RESTART
>
> &OT
>
> ALGORITHM IRAC
>
> ORTHO_IRAC POLY
>
> ENERGY_GAP 0.001
>
> LINESEARCH 2PNT
>
> MINIMIZER CG
>
> PRECONDITIONER FULL_ALL
>
> &END OT
>
> &OUTER_SCF T
>
> EPS_SCF 1.0000000000000000E-07
>
> MAX_SCF 50000
>
> OPTIMIZER DIIS
>
> &END OUTER_SCF
>
> &END SCF
>
> &END DFT
>
>
> &SUBSYS
>
> &COORD
>
> Na 0.00000000 0.00000000 0.00000000 
>
> Na 0.00000000 2.81000000 2.81000000 
>
> Na 2.81000000 0.00000000 2.81000000 
>
> Na 2.81000000 2.81000000 0.00000000 
>
> Cl 2.81000000 2.81000000 2.81000000 
>
> Cl 2.81000000 0.00000000 0.00000000 
>
> Cl 0.00000000 2.81000000 0.00000000 
>
> Cl 0.00000000 0.00000000 2.81000000 
>
> &END COORD
>
>
> &KIND Na
>
> BASIS_SET DZVP-MOLOPT-SR-GTH-q9
>
> POTENTIAL GTH-PBE-q9
>
> &END KIND
>
> &KIND Cl
>
> BASIS_SET DZVP-MOLOPT-SR-GTH-q7
>
> POTENTIAL GTH-PBE-q7
>
> &END KIND
>
>
> &CELL
>
> ABC 5.62 5.62 5.62
>
> ALPHA_BETA_GAMMA 90.00000 90.00000 90.00000
>
> &END CELL
>
> &END SUBSYS
>
>
> &END FORCE_EVAL
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20190108/e8193a47/attachment.htm>