CCL:G: Gaussian 09 and 16 compared for mundane calculations


My institution has both Gaussian 09 and Gaussian 16, and I'm trying to decide which to use for my new project.  (My background is in applications of MD simulations, and I'm quite new to quantum chemistry.)  One reason to use 16 is that, well, it's the latest version.  One reason to use 09 is for consistency; it's been used in our group a lot in the past.

My colleague said he observed some different results from 09 and 16, though he didn't remember how large the differences were.  

I will likely do some of my own comparisons, but I am curious, does anyone have experience with this?

The calculations I will be doing for my project are pretty mundane: using RHF to optimize geometry, and using MP2 to calculate the energy and extract charges with CHelpG.  The basis sets I will use are fairly pedestrian -- 6-31G(d), cc-pVTZ, etc -- nothing particularly exotic.  

From looking at this page ( ), it looks like Gaussian 16 mainly added new methods and basis sets.  I can imagine that algorithm improvements/tweaks (faster, more effective parallelization, etc) could give rise to some numerical differences, but I would not expect these differences to be terribly significant for most properties.  Is this your experience?

Thanks for your time,

Andrew DeYoung, PhD
Department of Chemistry
Carnegie Mellon University