Actually, a word related to <hilasterion>, <hilasmos>, occurs in 1
John 2:1, and is rendered "propitiation" in the KJV and NASB.
The most comprehensive treatment on this whole subject of which I am
aware (not to slight entries in Kittel or Brown) is found in what is
now an old work: _The Apostolic Preaching of the Cross_, by Leon
Morris (Eerdmans, late '50s I believe). Morris goes heavily into the
LXX background of the wordgroup, comparing it to the Hebrew
words that it translates, etc. I don't know if anything has replaced
it, although I don't think Morris represents the majority opinion in
his conclusion: namely, that "propitiation" is a proper translation
and that other alternatives tend to water down the meaning.
Morris's primary concern seems to be that other alternatives (at that
time the "expiation" of the RSV was the primary one) do not carry the
necessary implications of "turning away wrath" that he found inherent
in <hilasmos>/<hilasterion>. At the same time, Morris argued against
the idea that the words carried the pagan notions of capricious and
vengeful deities when used in the LXX and NT.
I think that Morris was responding to C.H. Dodd and others back then
who influenced the RSV's translation. I myself would be interested
in knowing if anything major has been done with this topic since
sola (scriptura + gratia + fide) = solus Christus,
-- Ron Henzel