Dear Joe,
Yes there are, for example GPAW is
written in Python. However, the choice of many QM programs to use Fortran is not
simply because they are "old" codes, many newer QM packages have
deliberately chosen Fortran over alternatives (e.g. C++). QM simulations are
computationally intensive, and Fortran is rather hard to beat performance-wise
-- though modern C++ compilers are competitive these days (albeit with compiler
development teams an order of magnitude larger than the corresponding Fortran
ones). Fortran also has many modern features which are still lacking in most
mainstream languages, for example partitioned global-address space
(coarrays).
I don't see much incentive to
move the millions of lines of Fortran into another language, but what is
becoming increasingly common is to develop a high-level software layer in
something else, usually Python, which allows more rapid prototyping and
development, whilst keeping all the numerically-intensive work in Fortran or
C++.
I'm confused about your Mac M1 chipset reference; how does this
relate to your Fortran question? There are good ARM Fortran compilers, if
that's what you're worried about.
All the
best,
Phil Hasnip