[Hayao]

I don't understand the quantum chemical calculations called "ELI (electron localization indicator)".

What is electron localization in the first place? How can you actually "localize" an electron unless hitting it with some particle? I thought it was supposed be more of probability density problem.

I know that it is somehow supposed to represent bonds and how electrons are placed.
I read a lot of papers regarding this, but I can't find anything more fundamental about it.

I don't understand how it works first of all. I heard it can be solved using any basis sets, HF, DTF, etc, but I don't understand what it "really" represents. It says about an electron pair against a reference electron, but I have no idea what's that supposed to mean. They also talk about same-spin pairs, but that's impossible due to pauli exclusion principle.

They also have ELI-D and ELI-A, and I don't understand the difference.
They also talk about electron "basins" but what does that supposed to mean?

I also don't know how to read the 3D color maps of ELI. What are the ELI numbers supposed to mean? I know that it takes a number from 0 and up, but what does high ELI number mean?

Also, ELI value looks opposite with "direct space" and "momentum space", but I don't even understand direct space and momentum space, and why the values are opposite.


It just doesn't add up inside my head. Someone please help me.

[Enthalpy]

Momentum space:
http://en.wikipedia.org/wiki/Position_and_momentum_space
you characterize a particle by the distribution of its momentum in 3D. This distribution is the Fourier transform of the (complex in 3D) distribution of its position; the latter is the most usual expression of the wavefunction, that is, as a function of the position.