**Theory of high- T_{C} Superconductivity: Transition temperature**, D. R. Harshman, A. T. Fiory and J. D. Dow [arXiv]

It is demonstrated that the transition temperature (

*T*

_{C}) of high-

*T*

_{C}superconductors is determined by their layered crystal structure, bond lengths, valency properties of the ions, and Coulomb coupling between electronic bands in adjacent, spatially separated layers. Analysis of 31 high-

*T*

_{C}materials (cuprates, ruthenates, rutheno-cuprates, iron pnictides, organics) yields the universal relationship for optimal compounds, k

_{B}

*T*

_{C0}= β/ℓζ, where ℓ is related to the mean spacing between interacting charges in the layers, ζ is the distance between interacting electronic layers, β is a universal constant and T

_{C0}is the optimal transition temperature (determined to within an uncertainty of ± 1.4 K by this relationship). Non-optimum compounds, in which sample degradation is evident, e.g. by broadened superconducting transitions and diminished Meissner fractions, typically exhibit reduced

*T*

_{C}<

*T*

_{C0}. It is shown that

*T*

_{C0}may be obtained from an average of Coulomb interaction forces between the two layers.

D. R. Harshman, A. T. Fiory and J. D. Dow, J. Phys.: Condens. Matter. **23**, 295701 (2011); Corrigendum, J. Phys.: Condens. Matter **23**, 349501 (2011). This work is also listed in J. Phys.: Condens. Matter Highlights of 2011.