Dear CP2K community,<div><br /></div><div>I'm trying to learn how to calculate polarization using CP2K. I'm using 2x2x2 supercell of BaTiO3 to benchmark the polarization values compared to other references and Quantum Espresso. </div><div><br /></div><div>I'm using Berry phase method by setting <font color="#000000"><b>PERIODIC .TRUE. in MOMENTS</b><b> </b></font>as it's periodic system. And the output for the cubic structure looks like:</div><div><font color="#808080"> Dipole vectors are based on the periodic (Berry phase) operator.<br /> They are defined modulo integer multiples of the cell matrix [Debye].<br /> [X] [ 38.42563418 0.00000000 0.00000000 ] [i]<br /> [Y]=[ 0.00000000 38.42563418 0.00000000 ]*[j]<br /> [Z] [ 0.00000000 0.00000000 </font><font color="#008000">38.65618798</font><font color="#808080"> ] [k]<br /> Dipole moment [Debye]<br /> X= -0.1123396E-09 Y= -0.1123351E-09 Z= </font><font color="#008000">-0.1414722E-09</font><font color="#808080"> Total= 0.0000000</font><br /></div><div><br /></div><div>How I have been calculating the polarization value is: 1) As I'm only interested in the polarization in z direction, I combined the two values highlighted in green. And 2) I divide the values by the cell volume. 3) I convert the unit to uC/cm^2. The issue with this method is that the polarization of the cubic phase is not zero. I've been trying to figure this out because the polarization value for cubic phase should be zero or close to zero. And the zero polarization for cubic phase is reproduced by Quantum Espresso:</div><div> <font color="#808080"> VALUES OF POLARIZATION<br /> ~~~~~~~~~~~~~~~~~~~~~~<br /> The calculation of phases done along the direction of vector 3<br /> of the reciprocal lattice gives the following contribution to<br /> the polarization vector (in different units, and being Omega<br /> the volume of the unit cell):<br /> P = 0.0000000 (mod 30.0953409) (e/Omega).bohr<br /> P = 0.0000000 (mod 0.0088327) e/bohr^2<br /> P = 0.0000000 (mod 0.5053585) C/m^2<br /> The polarization direction is: ( 0.00000 , 0.00000 , 1.00000 )</font><br /></div><div><br /></div><div><br /></div><div>What I'm confused with is that the difference between the values in the dipole vectors and the dipole moment. Is either of them electronic polarization (from Berry phase) and ionic polarization? Or is the dipole moment in the bottom line calculated from the addition of the electronic polarization (Berry phase) and the ionic polarization? Is there any reference/literature that describes how CP2K operates the Berry phase calculation?</div><div><br /></div><div><br /></div><div>Here's my input script:</div><div><font color="#808080">&GLOBAL<br /> PROJECT BTO<br /> RUN_TYPE CELL_OPT<br /> PRINT_LEVEL MEDIUM<br />&END GLOBAL<br /><br />&FORCE_EVAL<br /> ! This one is used for cell optimization<br /> STRESS_TENSOR ANALYTICAL<br /> METHOD QS<br /> &SUBSYS<br /> &KIND Ba<br /> ELEMENT Ba<br /> BASIS_SET DZVP-MOLOPT-PBE-GTH-q10<br /> POTENTIAL GTH-PBE-q10<br /> &END KIND<br /> &KIND Ti<br /> ELEMENT Ti<br /> BASIS_SET DZVP-MOLOPT-PBE-GTH-q12<br /> POTENTIAL GTH-PBE-q12<br /> &END KIND<br /> &KIND O<br /> ELEMENT O<br /> BASIS_SET DZVP-MOLOPT-PBE-GTH-q6<br /> POTENTIAL GTH-PBE-q6<br /> &END KIND<br /> &CELL<br /> A 8.000000000 0.000000000 0.000000000<br /> B 0.000000000 8.000000000 0.000000000<br /> C 0.000000000 0.000000000 8.000000000<br /> PERIODIC XYZ<br /> &END CELL<br /> &TOPOLOGY<br /> COORD_FILE_FORMAT pdb<br /> COORD_FILE_NAME BTO.pdb<br /> &END<br /> &END SUBSYS<br /> &DFT<br /> BASIS_SET_FILE_NAME BASIS_MOLOPT_UZH<br /> POTENTIAL_FILE_NAME GTH_POTENTIALS<br /> &QS<br /> METHOD GPW<br /> EPS_DEFAULT 1.0E-12<br /> &END QS<br /> &POISSON<br /> PERIODIC XYZ<br /> PSOLVER PERIODIC<br /> &END<br /> &XC<br /> &XC_FUNCTIONAL<br /> &PBE<br /> &END PBE<br /> &END<br /> &VDW_POTENTIAL<br /> POTENTIAL_TYPE PAIR_POTENTIAL<br /> &PAIR_POTENTIAL<br /> PARAMETER_FILE_NAME ../../dftd3.dat<br /> TYPE DFTD3(BJ)<br /> REFERENCE_FUNCTIONAL PBE<br /> &END<br /></font></div><div><font color="#808080"> &END VDW_POTENTIAL<br /> &END XC<br /> &MGRID<br /> NGRIDS 4<br /> CUTOFF 600<br /> &END MGRID<br /> &SCF<br /> SCF_GUESS ATOMIC<br /> EPS_SCF 1.0E-8<br /> MAX_SCF 300<br /> &MIXING<br /> METHOD BROYDEN_MIXING<br /> ALPHA 0.2<br /> BETA 1.5<br /> NBROYDEN 8<br /> &END MIXING<br /> &END SCF<br /> &PRINT<br /> &MO_CUBES<br /> WRITE_CUBE .FALSE.<br /> NHOMO 1<br /> NLUMO 1<br /> &END MO_CUBES<br /> &MOMENTS MEDIUM<br /> PERIODIC T<br /> &END MOMENTS<br /> &END PRINT<br /> &END DFT<br /> &PRINT<br /> &FORCES ON<br /> &END FORCES<br /> &END PRINT<br />&END FORCE_EVAL<br /><br />&MOTION<br /> &CELL_OPT<br /> TYPE DIRECT_CELL_OPT<br /> MAX_ITER 300<br /> OPTIMIZER BFGS #Most efficient minimizer, but only for 'small' systems<br /> &END CELL_OPT<br /> &GEO_OPT<br /> MAX_DR 0.003<br /> MAX_FORCE 0.00045<br /> RMS_DR 0.0015<br /> RMS_FORCE 0.0003<br /> MAX_ITER 200<br /> OPTIMIZER BFGS<br /> &BFGS<br /> TRUST_RADIUS 0.25<br /> &END BFGS<br /> &END GEO_OPT<br />&END MOTION</font><br /></div><div><br /></div><div><div>Here's the input structure:</div><div><font color="#808080">CRYST1 8.000 8.000 8.000 90.00 90.00 90.00 P 1 1<br />ATOM 1 Ba BTO A 1 0.000 0.000 0.000 1.00 0.00 Ba<br />ATOM 2 Ti BTO A 1 2.000 2.000 2.000 1.00 0.00 Ti<br />ATOM 3 O BTO A 1 0.000 2.000 2.000 1.00 0.00 O<br />ATOM 4 O BTO A 1 2.000 0.000 2.000 1.00 0.00 O<br />ATOM 5 O BTO A 1 2.000 2.000 0.000 1.00 0.00 O<br />ATOM 6 Ba BTO A 1 0.000 0.000 4.000 1.00 0.00 Ba<br />ATOM 7 Ti BTO A 1 2.000 2.000 6.000 1.00 0.00 Ti<br />ATOM 8 O BTO A 1 0.000 2.000 6.000 1.00 0.00 O<br />ATOM 9 O BTO A 1 2.000 0.000 6.000 1.00 0.00 O<br />ATOM 10 O BTO A 1 2.000 2.000 4.000 1.00 0.00 O<br />ATOM 11 Ba BTO A 1 0.000 4.000 0.000 1.00 0.00 Ba<br />ATOM 12 Ti BTO A 1 2.000 6.000 2.000 1.00 0.00 Ti<br />ATOM 13 O BTO A 1 0.000 6.000 2.000 1.00 0.00 O<br />ATOM 14 O BTO A 1 2.000 4.000 2.000 1.00 0.00 O<br />ATOM 15 O BTO A 1 2.000 6.000 0.000 1.00 0.00 O<br />ATOM 16 Ba BTO A 1 0.000 4.000 4.000 1.00 0.00 Ba<br />ATOM 17 Ti BTO A 1 2.000 6.000 6.000 1.00 0.00 Ti<br />ATOM 18 O BTO A 1 0.000 6.000 6.000 1.00 0.00 O<br />ATOM 19 O BTO A 1 2.000 4.000 6.000 1.00 0.00 O<br />ATOM 20 O BTO A 1 2.000 6.000 4.000 1.00 0.00 O<br />ATOM 21 Ba BTO A 1 4.000 0.000 0.000 1.00 0.00 Ba<br />ATOM 22 Ti BTO A 1 6.000 2.000 2.000 1.00 0.00 Ti<br />ATOM 23 O BTO A 1 4.000 2.000 2.000 1.00 0.00 O<br />ATOM 24 O BTO A 1 6.000 0.000 2.000 1.00 0.00 O<br />ATOM 25 O BTO A 1 6.000 2.000 0.000 1.00 0.00 O<br />ATOM 26 Ba BTO A 1 4.000 0.000 4.000 1.00 0.00 Ba<br />ATOM 27 Ti BTO A 1 6.000 2.000 6.000 1.00 0.00 Ti<br />ATOM 28 O BTO A 1 4.000 2.000 6.000 1.00 0.00 O<br />ATOM 29 O BTO A 1 6.000 0.000 6.000 1.00 0.00 O<br />ATOM 30 O BTO A 1 6.000 2.000 4.000 1.00 0.00 O<br />ATOM 31 Ba BTO A 1 4.000 4.000 0.000 1.00 0.00 Ba<br />ATOM 32 Ti BTO A 1 6.000 6.000 2.000 1.00 0.00 Ti<br />ATOM 33 O BTO A 1 4.000 6.000 2.000 1.00 0.00 O<br />ATOM 34 O BTO A 1 6.000 4.000 2.000 1.00 0.00 O<br />ATOM 35 O BTO A 1 6.000 6.000 0.000 1.00 0.00 O<br />ATOM 36 Ba BTO A 1 4.000 4.000 4.000 1.00 0.00 Ba<br />ATOM 37 Ti BTO A 1 6.000 6.000 6.000 1.00 0.00 Ti<br />ATOM 38 O BTO A 1 4.000 6.000 6.000 1.00 0.00 O<br />ATOM 39 O BTO A 1 6.000 4.000 6.000 1.00 0.00 O<br />ATOM 40 O BTO A 1 6.000 6.000 4.000 1.00 0.00 O<br />END</font><br /></div><div><br /></div><div><br /></div><div>Any of your inputs would be greatly appreciated. Thank you for your time and consideration in advance.</div><div><br /></div><div>Best, </div><div>Sue</div></div>
<p></p>
-- <br />
You received this message because you are subscribed to the Google Groups "cp2k" group.<br />
To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>.<br />
To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/d69b786c-2b3e-47be-bada-caef6b123f7dn%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/d69b786c-2b3e-47be-bada-caef6b123f7dn%40googlegroups.com</a>.<br />