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

[Henrique Junior]

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
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