Notes on superconducting hydrides.

In their article "The quest for room-temperature superconductivity in hydrides" ( I Physics Today i , May 2019, page 52), Warren Pickett and Mikhail Eremets commented that "in the late 1960s William McMillan of Bell Labs extended the [Bardeen-Cooper-Schrieffer] analysis to moderately strong coupling", which is measured by the electron-phonon coupling constant, . Specifically, McMillan realizes that I T i SB c sb from his equation declines when, on average, the phonon frequency becomes either too large or too small and searching for maximum I T i SB c sb leads to I i = 2. Since in 1968 it was believed that I T i SB c sb = 7.2 K and I i = 1.3 in Pb, McMillan concludes that I T i SB c sb may reach 9.2 K in a Pb alloy when I i = 2.8. [Extracted from the article]