In my research, I use the CASTEP package in Materials Studio.
(The functional is GGA-PBE)
I doped the transition metals (Pd, Pt) on the g-C3N4 sheet for enhancing hydrogen adsorption.
The attached file is the EDDM results.
It doesn't fit the bader charge results which I calculated by den2vasp.
The bader charge results is shown in below:
Pd: 0.0049 H: -0.3253 sheet: 0.3204
Pt: -0.0384 H: -0.8141 sheet: 0.8525
The Pd metal shows loss electrons. It is different to bader charge.
My calculation format of bader charge is
Charge difference=Charge (after)−Charge (before)
I want to ask:
1. Does the negative numerical in bader charge means loss or gain electrons?
2. Is the right format: Charge difference=Charge (before)−Charge (after) ?
3. Does the hydrogen dissociation phenomenon effect the charge?
Hey Alvin Chen
Quick check on your findings: for the Pd-system (left), both Bader and EDDM seem to agree for Pd and H. As for the sheet, it is hard to tell from the EDDM plot ~ it may be faint at this isosurface level. In the Pt-system, on the other hand, I see some discrepancy, like the blue isosurfaces (electron loss) surrounding Pt apparently contradict the electron gain obtained in Bader. One thing I know from experience that might be happening here ~ Pt may lose electrons locally (blue in EDDM) but gain overall (Bader) due to some charge redistribution from the sheet, so the net gain in Pt may come from regions not visible in this EDDM isosurface. And again, it is hard to tell from EDDM what's going on with the sheet at this isosurface level. You may wanna try adjusting the isosurface values or maybe project them onto a strategic plane targeting better visualization.
Addressing your questions at the end:
1. A negative Bader charge means electron gain, and positive means electron depletion, e.g., Pd: 0.0049 (Palladium is losing electrons).
2. Charge difference = Charge(after) − Charge(before) is the standard practice.
3. Shooting in the dark, I'd say so, due to the relative electronegativity of the elements involved.
Hope that helps,
Best,
Thank you for your valuable insights, your perspective is very helpful.
I set the position of this slice at the hydrogen atoms and metal, with the main focus on the hydrogen bond cleavage and the electron transfer after the hydrogen atom bond dissociation.
I have some questions regarding EDDM and Bader charge, so I have presented additional results, as shown in the attachment.
In this figure, the region surrounding the transition metal is blue (indicating electron loss), while the Bader charge result is negative. Does this contradict each other?
The bader charge results shown as below:
Pd: -0.6749 ; sheet: 0.6749
Pt: -0.5783 ; sheet: 0.5783
These are the results before and after metal doping. Since there is no metal before doping, I used the theoretical charge number of 10 for Pd and Pt as the reference.
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