Calculating the graphene C 1s core level binding energy

core-holes
core-holes

I have a new article just out, published as a Rapid Communication in Physical Review B. The work is a computational study co-authored with Duncan Mowbray and Mathias Ljungberg from San Sebastian, Spain, and Paola Ayala from Vienna.

As described in the post about my recent review article, X-ray photoelectron spectroscopy is an extremely useful tool for studying the composition of nanomaterials. However, to correlate measurements to actual atomic structures, we need to know their binding energies. In this work, we systematically calculate the core level binding  energy of graphene using two different methods, as described in the abstract:

X-ray photoelectron spectroscopy combined with first-principles modeling is a powerful tool for determining the chemical composition and electronic structure of novel materials. Of these, graphene is an especially important model system for understanding the properties of other carbon nanomaterials. Here, we calculate the carbon 1s core level binding energy of pristine graphene using two methods based on density functional theory total energy differences: a calculation with an explicit core-hole, and an all-electron extension of the delta self-consistent field (ΔSCF) method. We study systematically their convergence and computational workload, and the dependence of the energies on the chosen exchange-correlation functional. The ΔSCF method is computationally more expensive, but gives consistently higher C 1s energies. Although there is a significant functional dependence, the binding energy calculated using the PBE functional is found to be remarkably close to what has been measured for graphite.

You can find the article on the PRB website, or in manuscript form on arXiv.

2014 in review

The WordPress.com stats helper monkeys prepared a 2014 annual report for this blog. "Only three posts in 2014... let's see if I can do more in 2015."

Here's an excerpt:

A New York City subway train holds 1,200 people. This blog was viewed about 7,200 times in 2014. If it were a NYC subway train, it would take about 6 trips to carry that many people.

Click here to see the complete report.

"Could a quantum computer have subjective experience?" by Scott Aaronson

People who are into physics and follow blogs actively have surely ran into MIT physicist Scott Aaronson, probably most well known for his critiques of the alleged D-Wave quantum computer. More recently, Scott has been writing a lot about consciousness, but his latest post – prepared talk notes from the Quantum Foundations of a Classical Universe meeting – is a real doozy. It's a long read but well worth the trouble.

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Elsevier, academia.edu, and Berlin OA meeting

News from the open access front, Mike Taylor amongst others have drawn attention to Elsevier being busy shooting itself in the foot by issuing thousands of takedown notices to authors that had deposited manuscripts to the social network site Academia.edu. Of dubious practical value, the move has again drawn negative attention on the company, leading to renewed interest in joining the ongoing boycott.

Stephen Curry comments on this in a recent blog post, but also does an excellent job of summarizing the recent Berlin Open Access meeting, where many of the key players presented the current situation. I won't try to summarize the same information here – just go and read his blog.

Stuart Firestein: The Pursuit of Ignorance (TED talk)

[youtube=http://www.youtube.com/watch?v=nq0_zGzSc8g&w=600&h=450] In one of my new favorite TED talks, neuroscientist Stuart Firestein gives a supremely entertaining yet deep account on his view of what doing science actually is all about. He really captures some essential things that I think are difficult to convey to laypeople – or indeed for scientists themselves to explicitly recognize. He gives a number of great quotations I wasn't familiar with before:

Thoroughly conscious ignorance is a prelude to every real advance in science. -James Clerk Maxwell

Science is always wrong. It never solves a problem without creating 10 more. -George Bernard Shaw

Every answer given on principle of experience begets a fresh question. -Immanuel Kant

Firestein finishes with a poignant critique of the education system. Really, really recommend watching this.

Via Open Culture.