Each additional bond order adds one Tau-strand at decreasing efficiency
The Tau-strand accumulation law: bond enthalpy increases sub-linearly with bond order because each additional strand must fit within the compressed Tau-field of the previous. The accumulation factor approaches 2/3 — the binary-ternary ratio.
C=C (2 strands): 614 kJ/mol increment: +267 ratio: 1.770
C≡C (3 strands): 839 kJ/mol increment: +225 ratio: 2.418
Diamond vs graphite: the two register topologies of carbon
C = 2²×3 is the lowest-mass element with both binary and ternary dimensions. Si = 2²×7 has a boundary prime instead — rigid lattice, no flexible polymers. Carbon is the necessary scaffold for biological Tau-registers.
Diamond: all sp³, {2,3} tetrahedral closure — maximum Tau-density, hardest natural material. Graphite: sp², {3} trigonal + 1 delocalised Tau-mode — conductor, lubricant. Allotrope = register topology choice.