Today we had Dr. David Strubbe from the Grossman Group at MIT as a guest speaker in the Aspuru-Guzik group meeting. His talk about “Exciton self-trapping in the optical response of pentacene crystals from first principles” covered a very important topic for the Clean Energy Project. Here is the abstract of his presentation:

Pentacene is a prototypical organic semiconductor with optoelectronic and photovoltaic applications. It is known that the lowest-energy singlet excitation has a Stokes shift between absorption and emission of about 0.14 eV, but the deformation associated with this self-trapped exciton remains unknown. We begin with a calculation of the optical properties via the first-principles GW/Bethe-Salpeter (BSE) theory [ML Tiago, JE Northrup, and SG Louie, Phys. Rev. B 67, 115212 (2003); S Sharifzadeh, A Biller, L Kronik, and JB Neaton, Phys. Rev. B 85, 125307 (2012)]. We then study the self-trapping phenomenon via our reformulation of the Bethe-Salpeter excited-state forces approximation of Ismail-Beigi and Louie [Phys. Rev. Lett. 90, 076401 (2003)], which can describe the structural relaxation after optical excitation.

We might be able to recruit a new team member for the Harvard CEP crew - our first discussions with him were very exciting. We'll let you know how things turn out.

Great weather for the start into September – we hope you all have a great Labor Day weekend. In case you are heading out to do some shopping, here is some stuff to consider about the advertisements you are about to encounter. Enjoy!
http://xkcd.com/870/

I saw they were anticipating slow recovery (resolved now) due to having to move a terabyte of data. They have my sympathy...I don't like to backup to the same room where the computational systems are (all the eggs in one physical basket just means they all cook in the same fire) so I back up over NAS to a different physical location - which is oh, so slow for terabytes. Knowledge which causes me to a) laugh at concepts like "cloud storage", and b) pay attention to web stories like SmallNetBuilder's "How to build Fiber Channel SAN for $1000." And still leaves me hoping the hardware will "grow up" someday...even the speeds attained with that SAN system cause me to yearn for the day when you will be able to buy multiple terabyte solid state drives for a couple hundred bucks and so dump the bottleneck of mechanical drives.

Will it ever happen at a reasonable price for the consumer? Looking doubtful, since the industry seems to think they can make more money by selling the public effectively storage-less tablet devices and then forcing the use of remote storage on their clouds where they can both charge for that storage and harvest useful tidbits from your data.

We just completed the permanent data archive structure on jabba2 and 3 with about 210TB of data. Next step is a fresh backup copy of everything on tape. Unfortunately, the new FAS-RC tape robot has started acting up, but the customer service is already booked.