What a happy coincidence -if indeed it was- that #RealTimeChem week happened to coincide with the sixtieth anniversary of the three seminal papers published in Nature on this day back in 1953, one of which was co-authored by J. Watson and F. Crick; of course I mean the publication for the first time of the structure of deoxyribose nucleic acid, or DNA, as we now call it.
You can get the original Nature papers from 1953 here at: http://www.nature.com/nature/dna50/archive.html (costs may apply)
Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid 737
J. D. WATSON & F. H. C. CRICK
Molecular Structure of Nucleic Acids: Molecular Structure of Deoxypentose Nucleic Acids 738
M. H. F. WILKINS, A. R. STOKES & H. R. WILSON
Molecular Configuration in Sodium Thymonucleate 740
ROSALIND E. FRANKLIN & R. G. GOSLING
Nature’s podcast released two episodes (called ‘pastcast’) to celebrate DNA’s structure’s birthday, one of them is an interview with Dr. Raymond Gosling who in 1953 worked under Dr. Rosalind Franklin at King’s College London in diffractometry of biological molecules. If you haven’t listened to them you can get them here at nature.com/nature/podcasts. Of course, the history around the discovery of DNA’s structure is not without controversy and it has been long argued that the work of Franklin and Gossling didn’t get all deserved credit from Watson and Crick. In their paper W&C acknowledge the contribution of the general nature of DNA from the unpublished results by Franklin’s laboratory but that is as far as they went, they didn’t even mention photo 51 which Crick saw at Wilkins laboratory, who in turn got it from Gossling at Franklin’s suggestion. Still, no one can deny that the helical structure with which we are now familiar is their work, and more importantly the discovery of the specific pairing, which according to Gossling was a stroke of genious that probably couldn’t have happened in his own group, but without Franklin’s diffraction and Gossling’s crystallization there was little they could do. Details about the process used to crystallize DNA can be heard in the aforementioned podcast, along with an inspiring tale of hard work by Dr. Gossling. Go now and listen to it, its truly inspiring.
For me it was not the story of a helix, that I was familiar with; it was the story of the specific pairing of two hélices
- Dr. Raymond Gosling
Above, the iconic Photo 51 taken by Franklin and Gossling (have you ever noticed how most scientists refer to Franklin just as Rosalind but no one refers to Watson as James? Gender bias has a role in this tale too) To a trained crystallographer, the helical symmetry is evident from the diffraction pattern but going from Photo 51 to the representation below was the subject of hard work too.
There are million of pages written during the last 60 years about DNA’s structure and its role in the chemistry of life; the nature of the pairing and the selectivity of base pairs through hydrogen bond interactions, an interaction found ubiquitously in nature; water itself is a liquid due to the intermolecular hydrogen-bonds, which reminds us about the delicate balance of forces in biochemistry making life a delicate matter. But I digress. Millions of pages have been written and I’m no position of adding a meaningful sentence to them; however, it is a fascinating tale that has shaped the course of mankind, just think of the Human Genome Project and all the possibilities both positive and negative! DNA and its discovery tale will continue to amaze us and inspire us, just like in 2011 it inspired the Genetech company to set a Guiness World Record with the largest human DNA helix.
Happy birthday, DNA!
Welcome of the third installment of #RealTimeChem, the diary. As I did yesterday and the day before, I will summarize my day in chemistry throughout the Tweets sent over this event.
— Joaquin Barroso (@joaquinbarroso) April 24, 2013
(Haha, I found the button to include the feed!)
I finally finished editing that supporting information I’ve been Twitting about all week, now I’m back at the manuscript re-editing a bit. This is a problem I have that I’m sure is shared by most of you: I just can’t let go. If I’m writing a manuscript I’ll read it and change it over and over; if I’m working on a presentation, I will edit and reorder the slides almost ad infinitum if it were not for deadlines. Professor Cea-Olivares, of whom I’ve written before in this blog, used to say that projects are never finished but merely abandoned. In all fairness we are still not on the ‘not letting go’ phase, there are still some sections of the manuscript that need our attention; and when I say we, I mean me and my collaborator Dr. Rodrigo Galindo who is currently working at the University of Utah (BTW go check out his blog and persuade him to pick it up again!)
But in the middle of the day there was a conference at Instituto de Química, in Mexico City, that I wanted to listen to. Dr. Marcos Hernández is a good colleague of mine who deals with asymmetric organocatalysis. I like his work a lot and I hold him in high esteem so I asked for a video transmission of his talk to be sent over to CCIQS at Toluca. In the following two Twits you can get a glimpse of our video conferencing facilities.
— Joaquin Barroso (@joaquinbarroso) April 24, 2013
— Joaquin Barroso (@joaquinbarroso) April 24, 2013
— Joaquin Barroso (@joaquinbarroso) April 24, 2013
Not all is work during RealTimeChem week, although perhaps it should be. Still, safety first! that’s our motto! (follow the link in message)
— Joaquin Barroso (@joaquinbarroso) April 24, 2013
Today I took some time to have a few interactions with other participants of #RealTimeChem and got to follow very interesting people. Definitely, after this week I will become a more active Twitter user (ouch!). But the research must go on, and today Maru started working on rendering the electrostatic potential surfaces for a rather large set of calix- and thiacalix[n]arenes for our line of research on molecular recognition agents.
— Joaquin Barroso (@joaquinbarroso) April 24, 2013
— Joaquin Barroso (@joaquinbarroso) April 24, 2013
— Joaquin Barroso (@joaquinbarroso) April 25, 2013
This is pretty much it for today; I’m very tired and I still need to work in other things so I’m off for now but stay tuned for more tomorrow when this blog will celebrate the 60th anniversary of the publication of DNA’s structure in Nature.
This initiative has turned out to be a lot of fun for me! I think so far the thing that has captured my attention the most is to grasp the realization that science, chemistry in this case, is performed by humans in small, and sometimes not so confident, steps, a description far from the pristine one we daily read throughout the plethora of journals. A similar former initiative, which should have been brought back during this week, was the #OverlyHonestMethods one. It’d be a lot of fun to have both hastags together during an entire week. The other thing I knew, but that #RealTimeChem has helped me understand is the fact that a lot of resources for research are needed and getting said resources consumes a lot of our time as researchers: grant submissions; applications revisions; meetings; academic events and a long etcetera occupy our time and attention and this isn’t necessarily a good thing all the time.
So here it is; my second day reporting my #RealTimeChem
Supporting information for our paper feels endless now. I want to launch calculations & I still have a ton of emails to reply!
Supporting information for our most recent paper consists of more than 200 figures corresponding to a few conformations from several compounds; this has consumed a lot of my time but I’m finally done with it! Now, its only a matter of time for us to submit it -we are aiming high!- and hopefully this may happen during #RealTimeChem. That would be cool!
No reply, unfortunately. I need to run some calculations for a small collaboration and these compounds include either La or Pr; I need a, preferably relativistic or quasirelativistic) effective core potential (maybe I should write a post illustrating the difference between ECP’s and pseudopotentials) for these atoms that is also compatible with some relatively simple electron density functional. The Basis Set Exchange library has one by Cao but its not referenced so there is only so much I can do with it.
Watching all the wheels of chemistry turn (slowly) during
#RealTimeChem makes you realize why each paper represents years of hard work
Between reading a Tweet about a grant submission and another one about having a paper published there is a lot of time and hard work involved, not to mention frustration, a little procrastination and a lot of fun over the course of a few years. During those years some chromatography columns are performed, some flasks are smashed and spectra are recorded. And this all happens very, very slowly as opposed as how we read it in journals where people seem to have had an original idea, gone to their labs, set up a few experiments, recorded the results and written the paper, and all before dinner!
The hindrances and intricacies of chemistry now have an outlet: blog-syn.blogspot.com In this site, the little details about synthesis are gathered in a sort of #OverlyHonestMethods way, only not as embarrassing; only practical. In a way, blog-syn is what this blog of mine was supposed to be for the lab of Dr. Silaghi-Dumitrescu back in Romania when I first conceived it. Little by little, the wheels of science turn but with every turn they move mankind forward.
Sadly, Maru is about to leave us for a short period of time now that she has completed her thesis and is about to get her B. Sc. in Chemistry; she threatens to come back for a Masters degree, though. She has played a crucial role in the lab’s success so I thought of taking a picture of her while working on her workstation. @RealTimeChem, the official Twitter account of the event, favorited this photo.
Tuesdays I teach a class titled ‘Molecular Design and Reactivity‘ (terrible name, I know) and today’s topic was the Valence-Bond method which, I’m sure you all know, is only of historical relevance although some nice conceptions arise from it, like the fact that a wavefunction can be approximated as a linear combination of smaller wavefunctions each corresponding to a specific electron configuration. I mostly use Donald McQuarrie‘s book on Quantum Chemistry, in case you are wondering.
This is a long three hours class starting at 5pm, and the research center is far from the chemistry school, so I usually don’t go back to the office afterwards. So here I am, at Starbucks in downtown Toluca, but chemistry for today is far from over! I still need to review some applications from students who are seeking funds from the local council for science to attend a seminar on polymers this summer in Barcelona. I was also requested by the Journal of Inclusion Phenomena and Macrocyclic Chemistry to serve as a reviewer for a submitted paper. Both activities have deadlines in May but I want to get them done now so I can
brag include them in my #RealTimeChem productivity report.
A few hours later…
Just Finished reading two proposals, I’m going to accept them both! 2 kids going 2 intl polymer seminar
And so I did it! Two students from a private university in the state want to participate in a polymer seminar in Spain. I think they have impressive results; too bad I had to sign a disclosure agreement so I can’t write anything about their project. Good for them and good for COMECyT for sponsoring outstanding students in science and engineering!
These past two days I haven’t personally launched any calculations; I haven’t had time to read any journals nor to write any applications or papers, yet I’m certain that the wheels at our lab are slowly turning, hopefully forward.
The first day of the #RealTimeChem event has gone by and here I am blogging about it in order to participate in the ensuing #RealTimeChemCarnival which is the blogging section, so to speak, of the aforementioned event. So, without further ado, this was my #RealTimeChem day:
Disclaimer: I’m not much of a Twitter man myself so I apologize in advanced for any dumb or stupid usage of it. I’m also new to Instagram and Vine, which I only downloaded on account of this event. Sorry for not taking snippets from the Twitter feed but I’m on Windows7 starter here and I don’t have such tools; I’m also not going to download some tool right now, sorry for that but if you know a better way, please do share it! I will be posting all week long so it might come in handy.
Editing sup. info. new paper on electronic interactions in rotaxane-like molecules with bio applications. Hope #RealTimeChem brings me luck!
We are almost done with this paper on drug delivery systems based on the architecture of calix[n]arenes. We’ve found some pretty interesting results about which features suit better certain drugs both in gas and solution phases. Most of my day had to do with editing the supporting information. Below, the picture that acompanied the previous Tweet.
Later on, along came a student whom, to be perfectly honest, I completely forgot about -my bad- but he was there and he was willing so off we went to work. Of course, being his first time, we had to start from scratch from the very basics of Gaussian’s use (and implicitly, the basics of the command line use in Linux). I’m not sure he wants his name to be posted here so he will remain in anonimity until otherwise stated. The associated Tweet read as follows:
Training a new student in using Gaussian, Gaussview and Linux. Lot of work to be done but he looks eager to learn
Being so much into #RealTimeChem worked as a serious motivator; the more you published the more you wanted to keep going! So all day long I had my head filled with things that I wanted to do, but I made a strong case about twitting only those things that I actually did and nothing in the lines of ‘thinking of …’ or ‘wishing I could…’ that sort of thing. I usually take little notes on google calendars about my day’s work as a means to keep track of my productivity, or sometimes, sadly, my lack thereof. This time Twitter was a loud witness of my activities which, hopefully, may be considered productive.
I teach a class on electronic structure each Tuesday, so I started preparing my class for tomorrow as a kind of break from editing that supporting information; the Twit read:
All day editing sup. info. has rendered me cross-eyed! Time 4 a break. Will reply work (chem) related email
and so I did. I got to reply to a professor in the far away island of Mauritius! He just invited me to participate in a virtual conference on computational chemistry. What a shame! It’d been nice to fly half way accross the world and set foot in that land! If you don’t know where Mauritius is, find Madagascar in southern Africa and then take a right on the Indic Ocean. As per his request, here I promote his event with all of you and with #RealTimeChem:
Then more e-mail
@joaquinbarroso 3h #RealTimeChem just accepted invitation 2 virtual conf.; accepted new intern by mail; now reviewing 2 applications for conference stipends
I didn’t finish reviewing these kid’s work but I think they might get their plane tickets from the local council for science and technology.
As I wrote earlier, I’m not a Twitter man so I get easily overwelmed by all the information generated within. I wanted to go home but before I got to read some Tweets and I was astonished by the enormous ammount of messages in the lines of ‘submitted a grant, now when can I do the corresponding research?‘; ‘grading! what a torture!’ and some others that indicated people was doing administrative work when they really wanted to get their hands dirty in the lab. This was a surprise to me because I imagined that most Twitter users and therfore, #RealTimeChem participants would be young students who are the ones who actually are up to their necks in chemistry! of course I Tweeted about my little observation in two messages.
So interesting 2 notice
#RealTimeChem deals more with research administration than wth research! I thought it’d be the other way around!
Having a new paper out is always fun and this week we got the wonderful news from the Journal of Physical Chemistry C that a paper I co authored with Prof. Alireza Badiei at the University of Tehran in Iran and his student, who actually got us all in touch, Dr. Pezhman Zarabadi-Poor, was accepted for publication.
The paper is titled “Selective Optical Sensing of Hg(II) in Aqueous Media by H-Acid/SBA-15: A Combined Experimental and Theoretical Study“; in it we explored the fluorescence quenching mechanism for a Hg(II) complex which forms the basis of a novel selective mercury detector. Geometry optimizations were carried out at the PBE0/6-31++G** PCM level of theory (along with the aug-cc-pVDZ-PP basis set and corresponding ECP for Hg), also the electronic spectrum of both the free acid and the Hg(II) complex was calculated.
(Frontier orbitals were depicted using Chemcraft)
We can observe that HOMO and LUMO+1 are mainly located on the naphtalene ring allowing for the S0 -> S1 transition and back, which accounts for the molecular fluorescence. Other internal conversion processes were also assessed and discussed in the paper which accounts for the quenching effect. In short, we have obtained a full quantum description of the mechanism by which coordination of the free acid to Hg(II) alters the ligand’s electronic structure converting its emisive lowest-lying excited state to a dark state, i.e., quenching! Pretty cool stuff!
Once again thanks to both Dr. Zarabadi-Poor and Prof. Badiei for thinking about me for collaborating with them in this joint endeavor which hopefully wont be our last. A PDF copy of the article is available by direct request through this post.
Thanks for reading, sharing, rating and commenting.
RealTimeChem, in its first week-long edition, is coming to your Twitter feed next Monday April 22nd 2013, and I for one intend to participate.
I look forward to this event in order to get in touch with other chemists, not only theoretical but experimental ones as well, around the world sharing a passion for chemistry and technology. I guess most of the participants will be experimental chemists who will amaze us with their videos and pictures of cool looking reactions; I hope we, here at our computational lab, are up to the challenge with our calculations.
Participating is really simple, just Tweet as little or as much as you want to share about your work or studies around chemistry under the #RealTimeChem hastag and follow @RealTimeChem. There is also a group and an event set up on Facebook, check those out too. As I write this, its Friday at 8:oo PM and I’m still in the office, which means I have a lot of work to do, therefore I don’t feel like writing about all the details of the event, specially when others have done so in a much more eloquently fashion: Check out these posts (as well as the entire content of their blogs, they’re very cool!) by Dr. Galactic and The Organic Solution for all the details about the event’s mechanics and, yes, even prizes to the best tweets.
So get on board and tweet all week long under the #RealTimeChem hashtag and share your work with the world the way no journal will ever do: in real time and with the uttermost embarrassing methodology honesty.
Thanks to Devang Sachdev from NVIDIA for bringing this webinar to my attention.
The future of computational chemistry seems to be written in CUDA for GPU’s specially when it comes to Molecular Dynamics; as such, NVIDIA has gone through great lengths into introducing scientific computing methods for GPU’s. I still have a pending review of a test drive that people at NVIDIA and EXXACTCORP kindly allowed me to run but that is the topic of the next post.
Next Thursday, April 4th, 2013 from 9:00 AM – 10:00 AM Pacific Standard Time there will be a webinar in which Dr. Erik Lindhal at Stockholm University and NVIDIA will discuss latest GPU-acceleration technologies available to GROMACS users; more specifically the latest accelerated version of GROMACS 4.6, which features are supported, it’s installation and use, and how it performs with latest NVIDIA Kepler GPUs.
Register here: http://goo.gl/0HtqJ
Please register and check your local timezone to avoid delays. I will register as soon as I finish typing this. Thanks once again to Devang Sachdev for all his help, patience and trust in this forum.
Here is a link to an article I was invited to write by my good old friend, Dr. Eddie López-Honorato from CINVESTAV – Saltillo; Mexico, for the latest issue of the journal ‘Ciencia y Desarrollo’ (Science and Development) to which he was a guest editor. ‘Ciencia y Desarrollo’ is a popular science magazine edited by the National Council for Science and Technology (CONACyT) of which I’ve blogged before.
This magazine is intended for people interested in science with a general knowledge of it but not necessarily specialized in any field. With that in mind, I decided to write about the power of computational chemistry in predicting some phenomena while shedding light in certain aspects of chemistry that are not that readily available through experiments. The article is titled ‘Chemistry without flasks: Simulating chemical reactions‘. The link will take you to the magazine’s website which is in Spanish, as is the article itself, and only to the first page; so, below I translated the piece for anyone who could be interested in reading it (Hope I’m not infringing any copyright laws!). Don’t forget to also check out Dr. López-Honorato’s blog on nuclear energy research and the development of materials for nuclear waste containment! Encourage him to blog more often by liking and following his blog.
Chemistry without flasks?
Typically we think of a chemist as a scientist who, dressed in a white robe and protected with safety glasses and latex gloves, busily working within a laboratory, surrounded by measurement equipment, glassware and bottles with colored substances; pours one substance onto other substance, transforming them into new substances while noting that the chemical reaction occurs through color changes, heat release , perhaps gas, and occasionally even an explosion.
Thus chemistry, the study of the material processing involves active experimentation to accomplish chemical reactions subsequently confirmed, although indirectly, that the changes have been conducted in the microscopic world, moreover, in the molecular and atomic world. The chemist plans these changes based on the knowledge he has of the chemical properties of the substances of which he started and, like any other substance, are due to its molecular structure, i.e., the spatial arrangement of the atoms that form it.
Under this archetypal image just posed, then it’s at least funny to think that there is a branch of chemistry named Theoretical Chemistry.
What is theoretical chemistry?
Theoretical chemistry is a kind of bridge between chemistry and physics; using laws and equations that govern the subatomic world, to calculate the molecular structure of a substance, more specifically calculate the distribution of electrons surrounding the molecule forming a cloud, which interact with the electron cloud of another molecule to form a new substance. It is based on the knowledge of the electron density cloud or we can understand and predict the chemical properties of any substance. We can then define theoretical chemistry as the set of physical theories that describe the distribution and properties of the electron cloud belonging to a molecule, in this particular mathematical description we call electronic structure and this is the starting point for descriptions and chemical predictions.
What is it good for?
Through theoretical chemistry we can find answers to fundamental questions about the structure of matter. Consider a molecule of water, which has the chemical formula H2O. This formula implies that there are two hydrogen atoms attached to an oxygen atom But what spacial structure does a water molecule have? The simplest geometry it could take would be a linear structure, in which the angle formed by the three atoms is 180 °. However, the water molecule has an angle of 109 °, far from a linear structure. In Figure 2 we can see the result of the calculation of the electronic structure of H2O, it observed that the electron cloud that exists on the oxygen atom also has a place in space and thus push the hydrogen atoms bringing them together instead of allowing them to take a more comfortable conformation.
Figure 2. Oxygen remaining electrons (red cloud around the oxygen atom) that are not chemically push the hydrogen atoms towards each other.
The industrial area currently impacted by the application of theoretical chemistry is the pharmacist, as they generate a new drug involves significant investment in financial and human resources, so predicting the properties of a molecule with pharmacological activity before synthesizing is highly attractive. Therefore it has been generated within the theoretical chemistry field, otherwise known as branch Rational Drug Design.
Drugs acting on our organism when active molecules interact directly with the various proteins which are distributed in the tissue cells. If the structure of the protein is known and we attack is known also a drug which acts on it, then we can design similar drugs having greater efficacy in the treatment of diseases. But it is not only fit one molecule to another, but to calculate the energy of interaction, the energy of dissolution and the probability that this interaction can be observed experimentally (Figure 3). The calculation of the interaction energy between the drug and the protein tells how strongly attract each other, a weak attraction drug will result in a low efficiency, while a greater attraction involve a more effective drug.
How do you calculate a molecule?
All matter exists in the universe is made of atoms, which in turn are composed of a nucleus of protons and neutrons surrounded by a cloud of electrons. When two or more atoms combine to form a molecule combining do their electron clouds and how do these combinations are best described by the equations of quantum mechanics, the branch of physics that describes the behavior of the subatomic world. However, due to its complexity, the equations of quantum mechanics can only be accurately resolved in the simplest cases such as the hydrogen atom, which consists of a single electron orbiting a proton. We must therefore resort to a range of methods and approaches to tackle cases of chemical interest and even biological.
For years the only available computers could solve the approximate equations for small molecules, no later than thirty atoms, which which can be interesting, but not entirely useful. Today modern supercomputing equipment (which may amount to up to tens or even hundreds of powerful computers connected together to work cooperatively) allow us to make models with hundreds of atoms molecules such as proteins or DNA fragments.
While the software available to perform these calculations is developed continuously for the last thirty years has been the progress in the design of computer systems able to perform thousands of operations per second the cornerstone that has made the theoretical chemistry a predictive tool commonly used. Today the branch known as Molecular Dynamics, which studies the interactions between molecules over time, has benefited from the development of the latest game consoles, as their processors, known as graphics processing units (GPUs , for its acronym in English) are able to perform calculations in parallel: Many of the images seen in our video games are actually calculated, not animated, this means that the console must calculate how to answer each item on the screen According to each stimulus we introduce. Conversely, if the images were animated, the answers would be always the same and the game would become unrealistic. Each game event should be calculated almost immediately to maintain its fluidity and emotion, in such a way that these GPUs have to be able to perform several mathematical operations simultaneously.
Traditionally molecular dynamics is based on the equations of classical physics, which only see the time evolution of molecules like solid objects collide, hundreds of molecules floating in water or other solvent. With the advent of GPUs can include dynamic calculating the electronic structure so we can peek into biological processes such as DNA replication or the passage of nutrients through a channel protein embedded in the membrane of a cell.
Since the fundamental understanding of the distribution of electrons in a molecule, its structure and properties to rational drug design, new materials based on molecular modeling theoretical chemistry is a powerful tool which is constantly progressing. The development of computer systems increasingly powerful detail allows us to meet the electronic processes involved in a chemical reaction while we can predict the real-time progress of molecular transformations. All this brings us ever closer to the dream of modern alchemists: transform matter to obtain substances with properties designed to pleasure.
In the nineteenth century, the American philosopher Ralph Waldo Emerson, wrote: “Chemistry was born from the dream of the alchemists to turn cheap metals into gold. By failing to do so, they have accomplished much more important things. ” And yes. Today we delve into the innermost secrets of nature not only to understand how it works but also to modify its operation on our behalf.
It’s been a long time since I last posted something and so many things have happened in our research group! I should catch up with them in short but times have just been quite hectic.
Here is a contribution from Igor Marques at the University of Aveiro in Portugal (Group Website); the original text can be found as a comment in the original NBO Visualization post but it is pretty much the same thing you can find in this post. Here is a link to Chemcraft’s website. Thanks for sharing this, Igor!
=> Examples provided by Igor Marques used Chemcraft Version 1.7, build 365 <=
In the Gaussian input, with the NBORead option included under the population keyword, we should include the PLOT option as illustrated below. The gfoldprint keyword will print the basis set to the output file in the old G03 format. Some visualization programs require a certain format of the basis set to be printed to the output file in order to plot orbitals and other surfaces like the electron density; therefore, if you want to play safe, use gfoldprint, gfprint and gfinput in the same line. gfprint will print the basis set as a list but in the new G09 format, whereas gfinput will print the basis set using Gaussian’s own input format. (The used level of theory and number of shared processors are shown as illustrations only; also the Opt keyword is not fundamental to the visualization of the NBO’s)
%chk=filename.chk %nprocshared=8 #P b3lyp/6-311++g** Opt pop=(full,nboread) gfoldprint filename 0 1 molecular coordinates $NBO BNDIDX PLOT $END
this will generate files from *.31 to *.41
For the visualization of NBOs, you’ll need FILE.31 and FILE.37. Open FILE.31 from chemcraft. It will automatically detect FILE.37 (if in the same directory).
Tools > Orbitals > Render molecular orbitals
select the NBOs of interest (whcih are in the same order of the output),
Adjust settings > OK
On the left side of the window, select the NBO of interest and then click on ‘show isosurface’. Adjust the remaining settings. To represent another orbital, click on ‘keep this surface’ and then select another orbital from the rendered set and follow the previous steps.
> It’s possible to open a formated checkpoint file, containing the NBOs, in chemcraft.
%Chk=filename.chk %nprocshared=4 #P b3lyp/6-311++g** Opt pop=(full,nboread,savenbo) gfoldprint filename 0 1 molecular coordinates $NBO BNDIDX $END
the procedure is identical, but it is only necessary to read the *fchk file and then render the desired orbitals.
However, two problems might arise:
a) Orbitals in the checkpoint are reordered, thus requiring some careful inspection of the output.
b) Sometimes, for a larger molecule, the checkpoint might not be properly saved and the Gaussian job (as previously reported – http://goo.gl/DrSgA ) will end with:
Failed in SchOr1 in NBStor.
Error termination via Lnk1e in /data/programs/g09/l607.exe at Wed Mar 6 15:27:33 2013.
As usual, thanks to all for reading/commenting/rating this and other posts in this blog!
How to calculate the Delta G of solvation? This is a question that I get a lot in this blog, so it is about time I wrote a (mini)post on it, and at the same time put an end to this posting drought which has lasted for quite a few months due to a lot of pending work with which I’ve had to catch up. Therefore, this is another post in the series of SCRF calculations that are so popular in this blog. For the other posts on this subjects remember to click here and here.
SMD is the keyword you want to use when performing a Self Consistent Reaction Field (SCRF) calculation with G09. This keyword was only made available in this last version of the program and it corresponds to Truhlar’s and coworkers solvation model which is recommended by Gaussian itself as the preferred model to calculate Delta G of solvation. The syntax used is the standard way used in any other Gaussian input files as follows:
# 'route section keywords' SCRF=SMD
Separately, we must either perform a gas phase calculation or use the DoVacuum keyword within the same SCRF input, and then take the energy difference between gas phase and solvated models.
# 'route section keywords' SCRF=(SMD,DoVacuum)
No solvation or cavity model should be defined since, by definition, SMD will use the IEFPCM model which is a synonym for PCM.
As opposed to the previous versions of Gaussian, the output energy already contains all corrections, this is why we must take the difference between both values (remember to calculate them both at the same level of theory if calculated separately!). Nevertheless, when using the SMD keyword we get a separate line, just below the energy, stating the SMD-CDS non electrostatic value in kCal/mol.
The radii were also defined in the original paper by Truhlar; I’m not sure if using the keyword RADII with any of its options yields a different result or if it even ends in an error. Its worth the try!
Some calculation variations are not available when using SMD, such as Dis (calculation of the solute-solvent dispersion interaction energy), Rep (solute-solvent repulsion interaction energy) and Cav (inclusion of the solute cavitation energy in the total energy). I guess the reason for this might be that the SMD model is highly parametrized.
Have you found any issue with any item listed above? Pleases share your thoughts in the comments section below. As usual I hope this post was useful and that you all rate it, like it and comment.