The "eV" (electronvolt) unit and its variants ("MeV", "GeV", "TeV", ...) are heavily used in nuclear and particle physics. By default Computer Modern and other common TeX fonts do not contain a pre-defined kern to pull the "e" and "V" closer together, presumably because that combination never occurs in "normal" written language.
While the amount of required kern is font-specific, and of course one can define
\eV etc. macros for use within a specific font, many physicists don't do so and hence end up with rather ugly units in their documents. Even the
siunitx package does not define its "eV" units with a negative kern (because of the font-specificity).
To make the problem less visible, while not solving it perfectly for every font, I wonder if it is possible to define a default e-V-negative-kern in a LaTeX style/class/preamble, so that documents written within a standard template will "automatically" acquire a better-than-default eV kern without the user needing to modify font metrics? Maybe in LuaTeX?
\XeTeXintercharclassand family. You can search this site for examples.
\eVas a macro to expand to
e\kern <some amount>Vor using
siunitxas a unit with the same set up. (Indeed, that's more-or-less what I'd expect people to do with
siunitx: as it's a design judgement I'm very wary of providing defaults or trying to pick up even a subset of fonts, though that is doable.)