Consistency can be evaluated with the so-called sum rules, which are integrals of the optical constants of a material in the full spectrum. Standard sum rules can help detect inconsistency of the optical constants but cannot say what specific spectral range(s) is responsible of such inconsistency. A new sum-rule procedure has been developed to evaluate the consistency at each specific spectral range with the use of window functions [1] and [2].
Example of a Window Function
Consistency evaluation parameter ζ of SiO2 optical constants. Five sum rules were used, which includes the indicated energy power. Parameter ζ comfortably stands within the ±0.005 limits in the whole spectral range for all five sum rules, which indicates that the optical constants are locally consistent in this wide spectrum. The exception is E2-sum rule in the limit of high-energy windows, where it diverges, what is attributed to limited precision in sum-rule calculations.