Cnoidal wave is the wave height, "λ" is the wavelength, "c" is the phase speed and "η" is the trough elevation. Further cn is one of the Jacobi elliptic functions and "K"("m") is the complete elliptic integral of the first kind; both are dependent on the elliptic parameter "m". The latter, "m", determines the shape of the cnoidal wave. For "m" equal to zero the cnoidal wave becomes a cosine function, while for values close to one the cnoidal wave gets peaked crests and (very) flat troughs. For values of "m" less than 0.95, the cnoidal function can be approximated with trigonometric
Madelung constant Madelung constant allows for the calculation of the electric potential "V" of all ions of the lattice felt by the ion at position "r" where "r" =|"r" - "r"| is the distance between the "i"th and the "j"th ion. In addition, If the distances "r" are normalized to the nearest neighbor distance "r" the potential may be written with formula_3 being the (dimensionless) Madelung constant of the "i"th ion The electrostatic energy of the ion at site formula_5 then is the product of its charge with the potential acting at its site There occur as many Madelung constants formula_3 in