Why the charge is zero?

Bader charge density analysis

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Why the charge is zero?

Post by Alex-LW »

Dear sir,
I use CP2K to analyze the electron structure of amorphous SiO2.I set the basis set and pseudopotential of the two elements to be DZVP-MOLOPT-SR-GTH and GTH-PBE-q6(GTH-PBE-q4). When I run bader code to analyze cp2k-ELECTRON_DENSITY.cube, the ACF.dat shows the CHARGE of O is around 8, and the CHARGE of Si is 0.000. The MIN DIST and ATOMIC VOL of Si are also 0.000. However the output of Mulliken Population Analysis shows the net charge of O is around -0.464 and the net charge of Si is around 0.925.
I also increase the FFT grid, but it doesn't work.I wonder why the result of Si is zero.
Thanks in Advance.
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Re: Why the charge is zero?

Post by graeme »

My guess is that you need core charge for Si. If you only have valance electrons, there may be no charge density maxima at the Si atoms. I am not a CP2K expert, however, but my recommendation is to see if you can get the total charge.

There is some discussion about this here: https://groups.google.com/g/cp2k/c/Yrnjqp2tBxs
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Re: Why the charge is zero?

Post by Al-chemist »

Dear graeme,

Unfortunately, this link is not accessible. I tried the web archive but could not find it, can you please suggest an accessible link?

I am facing a similar issue for two H atoms (belonging to a big organic molecule on a surface) with zero charge and volume. Both form N(-H)2 bonds with H...Halogen (2.53 Ang length and charge on the Halogen -0.57e, nothing extraordinary) and H...pi (2.43 Ang length and charge on the nearest C atom -0.26e, on the whole C4S ring -0.16e) bonds. How physical is this result? Can it be interpreted as almost full electron transfer from H atoms if charge density around them is < 0.0001 a.u. and not seen (generated with Quantum Espresso. i.e. with pseudopotentials for 1 valence electron in H atoms)?

Thank you in advance.
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