contact potential difference (Volta potential difference)

https://doi.org/10.1351/goldbook.C01293
The @E01935@ difference between one point in the vacuum close to the surface of M1 and another point in the vacuum close to the surface of M2, where M1 and M2 are two uncharged metals brought into contact.
Source:
PAC, 1983, 55, 1251. (Interphases in systems of conducting phases (Provisional)) on page 1257 [Terms] [Paper]