Uni-grams
topic1 -scuba,water,vapor,diving
topic2 -dioxide,plants,green,carbon
You can use word2vec to get most similar terms from the top n topics abstracted using LDA.
LDA Output
Create a dictionary of bi-grams using topics abstracted (for ex:-san_francisco)
check http://www.markhneedham.com/blog/2015/02/12/pythongensim-creating-bigrams-over-how-i-met-your-mother-transcripts/
Then, do word2vec to get most similar words (uni-grams,bi-grams etc)
Word and Cosine distance
los_angeles (0.666175)
golden_gate (0.571522)
oakland (0.557521)
check https://code.google.com/p/word2vec/ (From words to phrases and beyond)