Capacitance-Bias Variation

[sergio]

Hi,
I have followed http://quantumwise.com/publications/tutorials/item/511-calculation-of-atomic-scale-capacitance
to reveal the Capacitance -Bias variation of a device structure. Using the mulliken-analysis, for my device, I have obtained the capacitance as +1.54625e-20 Farad. But when I have plotted Capacitance-Bias variation it gives a negative capacitance varying from approximately -2.0e-20 to -1.54625e-20. So it is almost bias independent and converged to the capacitance that I have obtained. But the variation is negative but should be positive, what is the mistake here? Thanks for your help.

[sergio]

Hi,

Sorry, is there anybody who can solve the problem that I have encountered?

Thanks,

[kstokbro]

You have some sign error, possibly because you need to multiply mulliken population with -e to get the charge?

[sergio]

Hi,

Thanks for your reply. Yes, it is a sign error. But I have directly followed your script where -e is used. Thus I must get a positive variation but I have obtained a negative one.