lördag 14 oktober 2023

Chemistry vs Quantum Mechanics

A basic mantra of modern physics is that standard quantum mechanics stdQM as the physics of atoms can explain chemistry as the physics of molecules, by the fact that the stdQM Schrödinger wave function $\Psi (x1,...,xN)$ for an atom/molecule with $N$ electrons contains everything there is to say about the atom/molecule and its interaction with other molecules as chemistry. But there is a (serious) caveat: $\Psi (x1,...,xN)$ cannot be computed because it depends on $3N$ space dimensions. Already $N=2$ presents a challenge and $N>6$ is beyond the capacity of any thinkable computer. 

The mantra that stdQM explains chemistry thus lacks real concrete support, as argued by e.g Eric Scerri. There is in fact a big leap from stdQM to chemistry in the sense that atomic kernels have individuality by position in space, and so also their surrounding electrons and connected molecules/chemistry, while electrons in stdQM lack individuality; they have no specific positions in space and are supposed to be identical. 

RealQM presents an alternative to stdQM in the form of a classical continuum model in 3 space dimensions where electrons have individuality by occupying different regions in physical space without overlap. RealQM is computable also for molecules with many electrons and so may have the capacity to explain chemistry.

Here you can follow RealQM for a Carbon2 molecule consisting of two kernels and 12 electrons.  

Here is Boron2 molecule with two kernels and 10 electrons. 

Recall that efforts to bring back stdQM to reality in 3d were made by Richard Bader with his Atoms in Molecules AIM theory and in Density Functional Theory DFT (Nobel Prize in Chemistry 1998) by integrating $\Psi (x1,...,xN)$ over all but one variable, however without electron individuality causing serious problems. 

Recall that the physical meaning of stdQM is still a mystery after 100 years of fruitless search and dispute, which can only mean that stdQM lacks (physical) meaning.

2 kommentarer:

  1. Maybe quantum computers could do the stdQM computations.

    SvaraRadera
  2. Quantum computers are based on stdQM and so lack realism.

    SvaraRadera