Dear All,
I am trying to compare charge difference values WITH the numbers I obtained when doing the Bader analysis.
More precisely I have adsorbed one monolayer (ML) of oxalic acid onto a Copper surface. Being interested in the charge variation upon adsorption I have calculated the charge difference ( rho_diff=rho(ML_on_Cu) - rho(ML) - rho(Cu) ) and after this I have used the ctotac.f script (provided by VASP) in order to get rho_diff along the axis perpendicular to the Cu surface. From this I estimate that after adsorption each Cu atom transfer to the O atom (from above) 0.1 electrons.
When doing the Bader analysis I have considered the ML_on_Cu and the ML in vacuum systems. I have used only the valence charge when doing the Bader anlysis (I had some difficulties in getting the core charge properly). Compairing the charges for the oxygen atoms of the ML_in_vaccuum with the charges of the O atoms when the ML is adsorbed I get that almost 0.2 electrons are transfered from a Cu to an O atom. This is however two times more than the value obtained before. (for all the 4 oxygen atoms which interact with the surface I get in the first case a charge transfer of 0.4e while when doing the Bader analysis 0.7e. In the first approach I get that ALL ALONG the axis perpendicular to the surface I have 0.7e transfered !!!!! ).
Could you help me to explain these differences ?
In case it helps I give bellow the ACF.dat files for the adsorbed and free ML.
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Adsorbed ML
Cu 1 4.0000 1.8182 0.0000 11.0028 1.1695 65.7901
Cu 2 4.0000 5.4546 0.0000 11.0030 1.1695 64.6645
Cu 3 4.0000 1.8182 2.5713 11.0028 1.1695 65.6607
Cu 4 4.0000 5.4546 2.5713 11.0030 1.1695 64.6831
Cu 5 5.2857 3.6364 1.2857 10.9783 1.1581 14.3880
Cu 6 5.2857 0.0000 1.2857 11.0507 1.1599 14.7847
Cu 7 5.2857 3.6364 3.8570 11.0507 1.1599 14.7851
Cu 8 5.2857 0.0000 3.8570 10.9783 1.1581 14.3497
Cu 9 6.5713 1.8182 0.0000 10.9834 1.1616 11.9717
Cu 10 6.5713 5.4546 0.0000 10.9835 1.1616 11.9724
Cu 11 6.5713 1.8182 2.5713 10.9835 1.1616 11.9724
Cu 12 6.5713 5.4546 2.5713 10.9833 1.1616 11.9713
Cu 13 10.4284 3.6364 3.8570 11.0460 1.1555 12.1201
Cu 14 10.4284 0.0000 3.8570 10.9597 1.1555 11.7746
Cu 15 10.4284 3.6364 1.2857 10.9595 1.1555 11.7739
Cu 16 10.4284 0.0000 1.2857 11.0458 1.1555 12.1194
Cu 17 11.6942 5.4479 5.1318 11.0024 1.1398 13.2545
Cu 18 9.1427 1.8393 5.1426 10.9992 1.1581 11.9998
Cu 19 11.6973 1.8254 5.1313 11.0039 1.1464 13.3175
Cu 20 9.1427 5.4336 0.0001 10.9993 1.1581 11.9971
Cu 21 11.6942 5.4617 2.5604 11.0025 1.1395 13.2541
Cu 22 9.1427 1.7971 2.5714 10.9989 1.1581 11.9983
Cu 23 11.6973 1.8112 2.5597 11.0042 1.1463 13.3213
Cu 24 9.1427 5.4757 2.5712 10.9995 1.1581 11.9979
Cu 25 12.9116 3.6395 3.8358 10.6950 0.8723 14.0194
Cu 26 7.8570 3.6362 1.3074 10.9865 1.1643 11.9743
Cu 27 12.9629 0.0021 3.8325 10.7094 0.8920 14.5220
Cu 28 7.8570 0.0002 1.2633 10.9956 1.1640 12.0055
Cu 29 12.9633 3.6351 1.2618 10.7091 0.8916 14.5213
Cu 30 7.8570 3.6367 3.8347 10.9956 1.1640 12.0055
Cu 31 12.9124 7.2697 1.2638 10.6950 0.8715 14.0262
Cu 32 7.8570 7.2726 3.8787 10.9865 1.1643 11.9743
C 33 15.4449 7.2424 0.0053 1.1717 0.0538 3.5712
C 34 15.4446 3.6710 2.5793 1.1774 0.0568 3.5826
C 35 17.0149 7.2322 0.1178 1.0830 0.0644 3.2443
C 36 17.0145 3.6836 2.6935 1.0784 0.0643 3.2307
O 37 14.9379 0.0060 3.9887 7.7343 1.0123 19.0803
O 38 14.8399 7.2150 1.1118 7.7675 0.9831 18.6855
O 39 14.9384 3.6353 1.4196 7.7280 1.0128 19.0882
O 40 14.8387 3.6952 3.6854 7.7696 0.9841 18.6836
O 41 17.6879 7.2361 4.1126 7.9592 1.0307 84.3651
O 42 17.5431 7.2227 1.2052 7.8857 1.0889 63.4584
O 43 17.6889 3.6801 1.5465 7.9572 1.0253 84.1263
O 44 17.5414 3.6942 3.7814 7.8911 1.0911 62.4179
H 45 17.1007 7.2440 3.3162 0.0000 0.0000 0.0000
H 46 17.1025 3.6715 0.7494 0.0000 0.0000 0.0000
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Free ML
1 15.4450 7.2426 0.0051 0.9966 0.0536 2.8966
2 15.4448 3.6709 2.5793 0.9990 0.0566 2.8947
3 17.0118 7.2325 0.1184 1.1272 0.0634 3.4759
4 17.0113 3.6835 2.6941 1.1570 0.0465 3.5207
5 14.9416 0.0063 3.9872 7.5716 1.0822 96.3167
6 14.8424 7.2151 1.1126 7.5801 1.0765 150.3375
7 14.9421 3.6352 1.4184 7.5680 1.0797 96.3668
8 14.8413 3.6950 3.6862 7.5818 1.0707 150.8454
9 17.6878 7.2363 4.1119 7.9266 1.0314 163.0604
10 17.5470 7.2231 1.2034 7.7981 1.0834 86.2731
11 17.6888 3.6799 1.5459 7.9305 1.0259 162.8645
12 17.5448 3.6940 3.7798 7.7637 1.0420 85.6524
13 17.0996 7.2441 3.3159 0.0000 0.0000 0.0000
14 17.1013 3.6713 0.7493 0.0000 0.0000 0.0000
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With all the best wishes,
Ed
Charge difference Vs Bader analysis
Moderator: moderators
Re: Charge difference Vs Bader analysis
To get accurate numbers, you should use core charges. Instructions for doing this are here:
http://theory.cm.utexas.edu/bader/vasp.php
I see that your H atoms have no Bader charge, which indicates that the core charge around those H atoms is not reproduced in your valance charge density. I don't know if you will get the same result between proper Bader charges and your z-integration method, but you should start with a proper Bader analysis and then see where you're at.
Make sure to use PAW potentials, and a version of vasp >=4.6.31
http://theory.cm.utexas.edu/bader/vasp.php
I see that your H atoms have no Bader charge, which indicates that the core charge around those H atoms is not reproduced in your valance charge density. I don't know if you will get the same result between proper Bader charges and your z-integration method, but you should start with a proper Bader analysis and then see where you're at.
Make sure to use PAW potentials, and a version of vasp >=4.6.31