# Why I am not using HyperChem

Dear CCL readers,
Due to current interest to HyperChem I decided to add my 0.02c.
Last year we had a chance to try HyperChem v 3.0. This programs has
good graphics and very good molecular editor/builder. Unfortunately, it
is very slow, at least for semiempirical calculations. For example,
it takes 35 min. on 486DX2 50MHz with 16 MB of memory to do MNDO 1SCF
and gradients for C60 (compare to Sibiq - 10 min.). We send to HyperChem
mail list a question 'why it is slow?', and the answer was "HyperChem
have not been optimized for speed". The second thing, which surprised us,
was that the best geometry optimization method we could choose was
conjugated gradients. This method not only 2-10 times more slow then
ordinary used in semiempirical calculation qusi-newton methods, but,
also, it may has a problem with convergence for a flat potential surface.
If someone is looking for program to do demonstration or teaching, HyperChem
is, probably, a way to go. I don't think that it is (sorry, was,
I am not sure that version 3 is the last version) a right choice to do
semiempirical calculations. It is, of course, my personal opinion.
Dr. Andrey Bliznyuk.