All I care is the real structure of atoms, may carbon or gold or hydrogen.

But you have asked for an explanation of the structure of a compound, not an atom.

Besides pulling out quantum laws, no one has an logical answer to:

What force keeps opposite charges apart as electron and proton in atoms?

Quantum laws. Logic, as perceived by most people, has very little to do with the reality of atomic physics.

Isn't force the mechanism for everything?

No. It's a macroscopic summation of the real mechanisms.

In science you have to start with what is, not what you think ought to be, and then work out how reality works.

Now let us suppose that we have six electrons that "want to be" as far from each other as possible, but in some way disposed around a nucleus. It turns out that two can occupy a spherically symmetric orbital, with paired spins. Now we need to distribute four in some sort of symmetry (because a symmetric structure will have the lowest energy). But there are other carbon atoms nearby, each with four outer electrons. So we can construct a 3-dimensional lattice in which pairs of electrons with opposite spins occupy orbitals aligned with the axes of tetrahedra with a nucleus at the center of each tetrahedron, and

*voila*, diamond.

Alas, this simple explanation involves paired spins, which is a quantum mechanical concept. However given that elementary quantum mechanics is over 100 years old and part of the school syllabus, I think we can be forgiven for using it. Especially as no other explanation works.