It seems a bit weird that there isn’t much information on this topic on the internet. Recently I’ve had to calculate some of these indices to explain an anomalous behaviour in lactones formation and out of curiosity I ran a small search on the net about how to calculate them.

It’s always hard to write about a computational method in a blog post since it could span for pages on end, so that’s why this post as the ones about NBO and PCM will only treat briefly the underlying physics (at a handwave level) and interpretation about the most popular choices within multiconfigurational methods which form part of the family of post Hartree-Fock methods*. If you are only interested in one of the many MC methods scroll down

After months of waiting I am now oficially hired as an associate researcher at the Chemistry Institute from the National Autonomous University of Mexico! Actually I will form part of the new Joint Center for Research in Sustainable Chemistry located outside the city of Toluca in Mexico. This new job comes as a great career opportunity in which long term perspectives are high.

Another common question on CCL… The use of Internal Redundant coordinates (through the Opt=ModRedundant option) must not be overlooked! This option performes a geometry optimization at each step while maintaining the scanned variable constant, which is referred to as a Relaxed Potential Energy Surface (PES) Scan. Using internal coordinates becomes compulsory and a well-defined Z-Matrix is preferable.

Way off topic post that I began writing around the last World Series in October 2009. ‘ Why do you like it? ‘ is the most recurrent question I get from my European friends and most in Mexico. The easy and short answer is because my dad got me into it since he likes it too. But what makes me keep on liking it? In few words I like it because it is complex.

In this new post I will address some issues regarding the correct use of the terminology used about basis sets in ab initio calculations. One of the keys to achieve good results in ab initio calculations is to wisely select a basis set; however this requires some previous insight about the specific model to use, the system (molecule/properties) to be calculated and the computational resources at hand.

Yesterday, on December 25th prof. Silaghi passed away. He leaves us all, his students, co-workers, friends and relatives with a deep hole in our hearts. We all witnessed what a hard year he had in terms of health and we are solely comforted by the thought of him not suffering anymore. I hereby send my condolences to his wife, children and grand children hoping they find comfort and peace.

This year went by in a heartbeat. A lot of things happened and some nice research was performed. I especially enjoyed the summer in Hungary and working at Pecsi Tudomanyegyetem.

I’m posting this white paper “as is” but I will keep on coming back to update it; the thing is that I haven’t had the time to post anything else lately and if I don’t do it like this then I will never get it out. Please be kind on your comments and ratings! For a more thorough discussion of NBO analysis please check out the references.

This is the second post on a series which will try to address common technical questions in computational chemistry that recursively appear on the CCL. The Natural Bond Orbitals analysis is a powerful tool in population analysis calculations which is more robust than the traditional Mulliken approach, if for no better reason because its almost insensitive to the change of basis set while Mulliken’s P.A. is highly sensitive to basis set effects.

My boss just told me a few days ago he may not be able to make it to a workshop in Bucharest, which is actually more of a bilateral conference between Romania and South Korea. So it seems I’m due up for making a presentation for this meeting on next Wednesday (that is the day after tomorrow!). The down side? I’m not available tomorrow (Sep.