Key Test: Why Does not Helium He form He2 Molecule?

The crown jewel of modern physics is Schrödinger's equation as a mathematical model describing the physics of atoms and molecules in a new form of mechanics named quantum mechanics fundamentally different from classical mechanics of macroscopic objects, which we refer to as Standard Quantum Mechanics StdQM. 

Schrödinger's equation was formulated in 1926 coming with the expectation that it would also cover chemistry as the physics of atoms and molecules, in particular the physics of chemical bonding when atoms combine to form molecules under release of energy on a path towards atomic energy minimization.  

But concrete results did not come easy because the Schrödinger equations showed very difficult/impossible to solve because of its many dimensions, and so could not really deliver new understanding of how chemical bonds are formed and so chemists continued to rely on heuristic models such as octet rule, Lewis Structure, Valence Shell Electron Pair Repulsion VSEPR, molecular orbital hybridization, and electronegativity. 

It appears that today the physics of chemical bonding, covalent or ionic or a mixture, is still not uncovered in the form of solutions of Schrödinger's equation, still impossible to solve without drastic simplification coming with unknown errors.

RealQM is a new alternative to StdQM as a form of classical continuum mechanics in 3 space dimensions, which is computable for atoms/molecules with many electrons. 

Let us now see what StdQM and RealQM have to say about the physics of a covalent bond between two Helium He atoms each with two electrons around a kernel of charge +2, formed by interaction between the electrons into a He2 molecule.  

A covalent bond will form if the total energy of He2 at some kernel distance of about 1 Å or 2 atomic units with substantial spatial presence of electrons from both atoms, is less than that of two separate He atoms.

StdQM tells that a covalent bond will not form, because it is prevented by strong repulsion between the electrons of one atom and those of the other, with reference to the Pauli Exclusion Principle. 

RealQM tells that there is no reason for a covalent bond to form since the energy of two He atoms stays essentially the same under approach until kernel repulsion makes it increase. 

To make a verdict between StdQM and RealQM, let us recall the following observations of release of energy in Hartree when elements in the 2nd row of the periodic table form diatomic molecules:

• Li2    E = 0.04
• Be2   E = 0.004
• B2     E = 0.061
• C2     E = 0.23
• N2     E = 0.360
• O2     E = 0.19
• F2      E = 0.059

We see a decrease towards zero as we move left in the table (up in the list) from maximal energy 0.360 for N2 to very small for Be2 and Li2, which extrapolates to 0 for He2. This fits with RealQM showing no change of energy of He2 under atomic approach as outlined in the two previous posts. Extrapolation down the list suggests 0 for Neon2. 

But it contradicts StdQM claiming strong electronic repulsion asking for strong input of energy.  

In short: RealQM gives no net electronic repulsion for He2, while StdQM gives strong electronic repulsion (of size 0.37-0.44 Hartree according to chatGPT web search).

Direct observation of the energy of He2 under approach is said to be difficult because of the assumed strong repulsion, and so is not available. But if there is no repulsion, then it should be possible to measure that as a null result.

We find a situation where observation gives indirect support to RealQM as no repulsion, rather than StdQM as strong repulsion. 

A direct experiment could give direct support to no repulsion, but no such experiment has been performed with the motivation that it would be impossible because of strong repulsion.  The experiment that could refute StdQM is thus deemed to be impossible, and so has not even been attempted. Or so it seems...

 

Can we ask experimenters to measure the electronic repulsion between He atoms? It does not appear to be difficult...