Regarding XDI files containing data as chi(k), chi(R), or Filtered[chi(k)]

[bruceravel]

This is one of a short string of issues I am opening up after doing some work on the specification document leading up to #28.

The table of array labels in the dictionary has entries for χ(k) and χ(R). It seems the k and r columns should have units. For k, this is presumably inverse Angstroms. For r, Angstroms, picometers, or nanometers (with Angstroms preferred).

Some questions:

1. Should Angstrom be spelled with or without diacritic marks over the "A" and "o"?
2. And should "inverse Angstrom" be two words with a space between, or a single word (either concatenated or with an underscore)?

Regarding 1, I suggest recognizing [ÅåAa]ngstr[öo]ms?

Regarding 2, The explanation of values with units in the dictionary, as written, is ambiguous as to whether the string explaining the units is a single word or may be multiple words. I propose "inverse
Angstrom" with the multiple spelling of Angstrom suggested above.

[newville]

Are you suggesting that XDI support unicode? Or is that "only" ISO-8859-1?
A PR that handles unicode (or even ISO-8859-1) in the C and Fortran readers would be nice.