True as far as it goes, and silent on what decides — page 3 of 3
Every claim that earns this verdict, in the form it is usually taught, with the computation that settles it. The other verdicts are indexed beside this one, and they are not interchangeable — which of them a claim earns is a statement about how it is wrong, and that is the part that generalises.
402 claims earn this verdict, 2 of them here, in the order of the essays that test them.
“A repulsion model with a lone pair as one more domain cannot represent xenon hexafluoride's distorted octahedron.”
With the domains alone it cannot: the pentagonal pyramid is the lowest structure at every lone-pair weight from 1.05 to 3. With a contact repulsion between the six fluorines it can: the capped octahedron takes over at 1.0, 2.3 and 4.4 per cent of the domain energy for weights of 1.2, 1.5 and 2 under Born–Mayer contacts, and at 0.4 to 1.8 per cent under fluorine's own 2p overlap. A stereochemically inactive lone pair remains outside it.
Tested in The lone pair goes through a face · the series on VSEPR
“Adding a repulsion between the ligands to the σ-only model can account for main-group square pyramids such as pentaphenylantimony's.”
Only a repulsion steeper than about the fifteenth power of the ligands' separation can. For 1/r, 1/r⁶ and 1/r¹² no weight up to a million times the bipyramid's σ cost gives a square pyramid at any σ parameter from 1 to 5; for 1/r¹⁶, 1/r²⁰ and 1/r³⁰ every one switches, at shares of 1,100, 230 and 100 at q = 2.
Tested in Only a steep contact makes five square · the series on hypervalency