If you write on Liszt's Spanish Rhapsody, you will mention the history of the traditional themes he has selected, maybe talk about that famous RH scale 123451234512345 and how it influenced Busoni's techinical innovations...
But generally, I think you will have a hard time writing a whole research paper specifically on Spanish Rhapsody. you will probably have to resort to talk about Liszt in general, rather than the single work.
If you have to do a research paper on a single composition, I would do Berlioz's Symphony Fantastique or Tchaikovsky's Romeo and Juliet overture.. -->these have stories directly linked to the music, and you will have much more to talk about.