Every few years, I give my laptop a fresh start and remove all the debris (applications, libraries, updates) that have built up. This time I started with a clean install of Mac OS 10.11 (El Capitan).
The first step is to install the essentials including Dropbox, Evernote, Todoist, Xcode (with xcode-select –install ), Slack, Mendeley, MS Office, gcc/gfortran. Python superpack. VESTA, Transmission, Mactex. Texmaker, Unrar. VLC, Adobe Creative Suite, iTerm. Textmate. XQuartz .
While it is possible to survive using gfortan and freely available maths libraries, Intel Fortran and MKL tend to be faster and better tested (easier to compile) in my experience. For non-commericial purposes Intel Composer is now free for OS X. The package installs in a few clicks, but be sure source the variables in your .bash_profile :
source /opt/intel/mkl/bin/mklvars.sh intel64
source /opt/intel/bin/ifortvars.sh intel64
Finally you will need to make the MKL fast fourier transforms (FFTs) for use in most solid-state simulation packages:
sudo make libintel64 CC=gcc
aron$ which ifort
aron$ ifort –version
ifort (IFORT) 16.0.1 20151020
To enable parallelism, I downloaded the latest source code of openmpi (1.10.1).
./configure -prefix=/usr/local/openmpi-1.10.1 CC=gcc FC=ifort F77=ifort
sudo make install
be patient… it can easily take 20 minutes. Finally add to your .bash_profile.
aron$ which mpif90
aron$ mpif90 –version
ifort (IFORT) 16.0.1 20151020
We use this open-source lattice-dynamics package a lot in our research. There are a few more libraries to install first:
sudo easy_install pip
pip2 install lxml
pip2 install pyyaml
then after expanding the source code. simply type:
python setup.py install
_ __ | |__ ___ _ __ ___ _ __ _ _
| ‘_ \| ‘_ \ / _ \| ‘_ \ / _ \ | ‘_ \| | | |
| |_) | | | | (_) | | | | (_) || |_) | |_| |
| .__/|_| |_|\___/|_| |_|\___(_) .__/ \__, |
|_| |_| |___/
If harmonic phonons are not enough for you, then Phono3py lets you calculate phonon-phonon interactions, but it gets very computationally expensive. We need to install hdf5 (for more efficient data management):
pip2 install h5py
and lapacke for faster code. Download the latest version of lapack and:
cp make.inc.example make.inc
Then you are ready to compile. Download Phono3py and modify setup3.py to link to your compiled lapacke library.
if platform.system() == ‘Darwin’:
include_dirs += [‘/Users/aron/Documents/progs/lapack/lapack-3.6.1/lapacke/include’]
extra_link_args = [‘/Users/aron/Documents/progs/lapack/lapack-3.6.1/liblapacke.a’]
python setup3.py install
_ __ | |__ ___ _ __ ___|___ / _ __ _ _
| ‘_ \| ‘_ \ / _ \| ‘_ \ / _ \ |_ \| ‘_ \| | | |
| |_) | | | | (_) | | | | (_) |__) | |_) | |_| |
| .__/|_| |_|\___/|_| |_|\___/____/| .__/ \__, |
|_| |_| |___/
While we use a range of electronic structure packages, VASP is the old reliable. I downloaded the latest version (5.4.1), which has streamlined the install process .
cp ./arch/makefile.include.linux_intel ./makefile.include
which needs to be modified to point to the correct compilers (here gcc, ifort and mpifort). We will also remove -DscaLAPACK from the precompiler options and set SCALAPACK =. There are now three patches/bug fixes to install:
patch -p1 patch.5.4.1.08072015
patch -p1 patch.188.8.131.52082015
patch -p1 patch.5.4.1.06112015
and one fix to sort out a gcc error. To the file ./src/lib/getshmem.c add one line at the end of the include statements :
#define SHM_NORESERVE 010000
Arons-Air-V:test aron$ mpirun -np 4. /vasp_std
running on 4 total cores
distrk: each k-point on 4 cores, 1 groups
distr: one band on 1 cores, 4 groups
using from now: INCAR
vasp.5.4.1 24Jun15 (build Jan 02 2016 21:20:37) complex
The atomistic simulation environment is a useful set of Python tools and modules. It now installs, including the gui, in two lines:
brew install pygtk
pip install python-ase
I will update with more codes and tools as I find time (posted in January; revised in July).
When I joined the University of Bath in 2011, I was greeted with an empty lab packed full of dusty worn out computers. I was alone for a few months before Lee Burton joined me for his PhD (he’s now at TIT ). Soon after, the number of computers and people grew. We expanded like an ideal gas to fill all available space across two offices.
This year the group dynamic was spirited with an almost overwhelming number of interesting projects and results. Some of the highlights were quantifying the internal dynamics of hybrid halide perovskites, to probing phonon-phonon interactions in semiconductors, and exploring linkage isomerism in molecular crystals. It has been really fun to benchmark our simulations against a range of techniques (I am excited about some inelastic X-ray and total scattering measurements coming up next year).
It takes some time to get used to research groups being in a constant state of flux. Chris Hendon graduated this year (he’s now at MIT ), while Adam Jackson and Federico Brivio are busy finalizing their theses. Clovis Caetano, who visited us from Brazil for one year, is getting ready to leave, while Suzy, Lucy and Dan are just starting their PhD adventures. There definitely is no routine to get bored by&… roll on 2016.
Over 2/3 of our publications are gold open access this year; the rest are green open access in the Bath repository .
Academics in the UK are just coming to terms with an open access policy for publications (from paid ‘gold’ to free ‘green’ university repositories).
What has received significantly less attention is the new UK research data policy. In my experience, raising this issue in conversation is met with blank expressions… what data policy?
Published research papers should include a short statement describing how and on what terms any supporting research data may be accessed.
The metadata must be sufficient to allow others to understand what research data exists, why, when and how it was generated, and how to access it.
My university, like most others, has put together policy and guidance documents but they are quite generic and don’t seem to have really filtered down to the researcher level.
In my field of computational materials science, there are now several options:
- GitHub my group has been using this a lot for research (DOIs can be generated via the EU-funded project Zenodo; 2GB limit per repository). Instead of building separate repositories for each paper, we have been collecting related information, e.g. Phonons and Crystal Structures .
- Mendeley Data a nice clean interface for uploading data and generating DOIs, but I haven’t seen any clear policy for storage limits or guaranteed data lifetimes.
- Figshare this repository plays nice with raw datasets and multimedia (e.g. a hybrid perovskite MD video ). The serious drawback is a 1GB storage limit (per free account) with a 250 MB file size limit.
- NoMaD a new respository to “host, organize and share materials data”. I have great hopes for this one, but at the moment the website is a little jaded, and the interface is light years behind the Materials Project (which serves a different purpose of being a single source database).
Ideally, a standard protocol would be adopted in the community to avoid the individual ‘data dumps’ that university repositories enable in favour of a systematic and searchable community database. Aiida allows one to do this at the research group or collaborator level, but I hope that NoMaD can build a critical mass of researchers (and sustained funding) to make this a reality.
The new academic year begins tomorrow, so I took a few days out to hang out in Dublin. It was nice meeting up with old friends and it gave some perspective on the years that have passed. In 2016 it will be a decade since I was awarded my PhD at Trinity College, and it will be the fifth and final year of my fellowship from the Royal Society.
In terms of research, I have a wonderful team producing plenty of interesting results, so my role has changed from coding and performing calculations to: (a) keeping a steady supply of good research projects; (b) maintaining funding and computer resources; (c) reading and editing manuscripts. I still try to keep Wednesdays free for book reading and personal projects. If I could shift the balance, I would prefer to spend more time writing (an activity which most scientists I know dislike, but which I find quite therapeutic).
I have haven’t been writing much here as mentally these tasks have been quite exhausting, so when I have free time I tend to write about movies, play on instagram. and try to learn Hangul. But I do have some good topics for posts in the near future!
It is a well-known fact that modern society consumes a lot of energy, and at a rapidly increasing pace. The annual primary energy consumption of the world in 2008 was estimated by BP’s 2009 Statistical Review of World Energy to be around 13.2 TW (the equivalent to around 11 gigatons of oil), a 30% increase from the previous decade. Of these 13.2 TW, less than 0.8 TW were generated by non-nuclear renewable energy sources . Solar energy is one of the many subsets of renewable energy, and it could possibly generate a significate portion of energy in places with increasing energy demand such as India, which stood at a 10.1% energy deficit in 2012 . However, with current solar technology, it is estimated that it would cost India at least $100 billion to deploy an infrastructure that could provide a significant amount of energy .
Cost-effectiveness is currently the biggest hurdle for solar energy, but new innovations in solar cell technology could clear the way towards an increased use of solar energy all around the world. Currently, the market is dominated by silicon-based solar cells, which occupy over 80% of the market share . Over the past few years, researchers have been shifting their focus towards thin-film solar cells using semi-conductors, which can absorb more light than their silicon-based counterparts. The main non-silicon based solar cells include: CdTe (Cadmium tellurium), CdS (Cadmium sulfide), CIGS (Copper indium gallium selenide), and CZTS (Copper zinc tin sulfide) cells . In order to figure out which of these solar cells is the best alternative, many factors must be taken into account. CZTS solar cells have specific characteristics that make them rise above other alternatives, and should be considered by engineers to be an important innovation in the field of renewable energy.
SEEKING ALTERNATIVES FOR PHOTOVOLTAIC CELLS
The current average cost of a kWh (kilowatt-hour) generated by solar energy in India is approximately 27 cents. This is much lower than the national average for all amounts of energy (6 cents/kWh). As a result, most of the energy from India is generated from sources others than solar energy, mainly oil and natural gas . How can engineers reduce the cost of solar energy? By increasing the efficiency of solar cells while maintaining or lowering their production cost. Copper zinc tin sulfide solar cells (known as CZTS cells) can be a reliable alternative to silicon-based solar cells that currently dominate the market. CZTS have three major advantages over the commercially available solar cells of today: Energy conversion efficiency, cost-effectiveness, and long-term durability.
Efficiency of CZTS Solar Cells
The first thing to consider in choosing the best possible solar cell is its efficiency in converting sunlight to electricity. CZTS cells are thin-film solar cells that work as a result of the photoelectric effect . They have been recognized as a promising alternative to current solar cells because of their “high absorption efficiency, direct band gap around 1.0 – 1.5 eV, and low toxicity” . Essentially, CZTS cells can convert a higher amount of energy from the sun into electricity in a smaller amount of space, which results in a higher energy output. Energy conversion averages surpass the 11% mark , with some theoretical estimates being as high as 27.5% . Comparing these with energy conversion theoretical limits for CdTe (12.5%) and CIGS (17.7%) cells , there’s evidence to support that CZTS solar cells are more efficient than other current models.
Cost Effectiveness of CZTS Solar Cells
In addition to the aforementioned high efficiency, there are other factors that must be taken into consideration when determining the most competent solar cell. The production cost of such technology is vital to their implementation at the large scale. When compared to other common types of solar cells (CdS, CdTe, and CIGS cells), CZTS cells are more cost-effective due to the natural abundance and price of their composing elements . CZTS cells are most closely related to CIGS cells in molecular structure, but have several key differences in composition.
Cadmium, indium, and gallium are rare, expensive elements. These are the main components in CIGS cells. To make a direct comparison, copper, zinc, and tin are common, inexpensive elements, and are the components in CZTS cells.
Long Term Durability of CZTS Cells
In addition to improved efficiency in energy conversion and cost, CZTS cells are also have another advantage over other types of solar cells: Sustainability. CdS and CIGS cells may provide short-term benefits, but CZTS cells are more stable due to their inorganic molecular structure , which results in more benefits in the long term. As a study peer-reviewed by Elsevier says, “Successfully addressing this problem is crucial, as a working device probably has to be stable during decades of operation to be economically competitive” . The optimal solar cell should be able to last a long time without being replaced, and many of the current solar cells suffer from this problem. One of the main problems with CIGS cells is that they are not very stable. The same study reviewed by Elsevier found that when exposed to water continuously while functioning, the film on the CZTS cells degraded significantly slower than the film in CIGS cells , which puts CZTS as a powerful competitor to other solar cells.
Personally, I think that long-term sustainability of solar cells is very important, because this would mean that existing infrastructures could be maintained at a reduced cost. There’s little benefit to installing a huge solar energy infrastructure that although less expensive, will require a lot of maintenance. Luckily, CZTS cells show promising amounts of longevity, which means that they could be implemented in big arrays and could be kept functioning for a long time without undergoing costly renovations.
IMPACT IN THE RENEWABLE ENERGY FIELD
If CZTS cells are able to meet their expectations when implemented at the large scale, they could have a large impact in renewable energy as a whole. Going back to the previous real-world situation, an estimate from a paper published by the Taylor & Francis group says that “within 15 years, there is a possibility of 42.3% reduction in capital cost of solar thermal power plants” in India, which would reduce their cost of solar energy to 14 cents per kWh . Although the cost is not as low as the average for other sources of energy, this is still a big step in the right direction towards a significant improvement.
In addition to aiding the mitigation of India’s power deficit, CZTS cells would increase the percentage of energy that comes from renewable sources. In 2014, about 84 percent of power generated in India came from non-renewable resources, which accounted for 34 percent of their greenhouse emissions . A shift towards renewable energy sources could not only help the citizens of India economically, but also environmentally. Looking at a long term impact, up to 30 percent of electricity in India could come from renewable sources by 2030, with a large portion of it coming from solar energy sources , should CZTS cells successfully reach full commercialization.
WHY CZTS CELLS HAVE A CONNECTION TO MY INTEREST IN ENGINEERING
CZTS cells hold a close connection to my interests in engineering because I am very passionate about sustainability and renewable energy. Since I was young, I’ve been involved in learning about the measures that humans have taken to reduce their increasingly concerning effect on the environment. I’ve become interested in renewable energy because I feel that the energy problem and its impact on the environment is one of the most important issues to solve in order to maintain a positive outlook on the future of society.
I think that another reason that I’ve been interested in renewable energy is because of my background. I was raised in the Dominican Republic in a rural area with an energy deficit, just like in India. Experiencing frequent power blackouts was not uncommon for me as I grew up. As a kid, I wondered where electricity came from and why it seemed like there wasn’t enough energy for everybody. Learning the basics about solar energy and photosynthesis fascinated me since plants, which we consider to be very inferior to us humans, have evolved to use the energy from the sun very efficiently. Meanwhile, humans have struggled to utilize the sun as a reliable, main source of energy.
Now that I’ve learned a lot more about these processes, I recognize that the processes that plants and photovoltaic cells use to draw energy from the sun are obviously very different, but I think that the analogy still stands. Solar energy has the potential to have a huge impact in our society, should engineers devote enough time and effort researching how to maximize its efficiency. CZTS cells seem to be a promising alternative to help solve one of society’s biggest problems, which is why I find them compelling as a future engineer.
One of the major problems in engineering today is to find a reliable, affordable source of renewable energy. CZTS cells are a new innovation that could be a huge step in solar energy. CZTS cells have improved efficiency, reduced cost, and their materials are available in increased abundance when compared to their competitors. All of these factors place CZTS cells as a viable alternative to current solar cell models, and could be implemented at a large scale to provide a significant amount of energy. Due to these reasons, I think that this is a huge innovation and is an important topic for engineers to discuss. In addition to a reduced environmental footprint and economical cost, an increased supply of renewable energy will definitely impact people’s lives personally. Places that suffer from energy deficits such as India would benefit the most from a solution in developing affordable solar energy, as this would improve the accessibility of energy to their citizens. Sunlight essentially hits everywhere on Earth, and the Sun is not bound to run out of energy any time soon, so I think that engineers should figure out how to capitalize on the energy from the Sun. Engineers of today and the near future should find importance in CZTS cells and spend more time trying to implement them all over the world.
- L. Peter. (2011, Apr. 4). “Towards Sustainable Photovoltaics: the Search for New Materials.” The Royal Society (online article). DOI: 10.1098/rsta.2010.0348
- S. Sundaray, T. Kandpal. (2013, Feb. 28). “Preliminary Feasibility Evaluation of Solar Thermal Power Generation in India.” International Journal of Sustainable Energy. (Online article). DOI: 10.1080/14786451.2013.770395
- A. Ghosh. (2015, Jun. 17). “The big push for renewable energy in India: What will drive it?” Bulletin of the Atomic Scientists. (Online article). DOI: 10.1177/0096340215590791
- I. Khalil, R. Bernasconi, L. Magagnin. (2014, Sept. 6). “CZTS Layers for Solar Cells by an Electrodeposition-Annealing Route.” Electrochimica Acta. (Online Article). DOI: 10.1016/j.electacta.2014.09.001
- B. Buyukebar, F. Ozel, H. Sakalak, H. Cavusoglu, M. Ersoz, M. Kus, M. Yavuz. (2015, Feb. 2). “A Comparative Study on Fabrication of Cu2ZnSnS4 (CZTS) Nanofibers Using Acetate and Chloride Metal Precursors.” Turkish Journal of Chemistry (Online Article). DOI: 10.3906/kim-1501-124
- Huanping Zhou, Wan-Ching Hsu, Hsin-Sheng Duan, Brion Bob, Wenbing Yang, Tze-Bin Song, Chia-Jung Hsu, Yang Yang. (2013, Jul. 25). “CZTS Nanocrystals: A Promising Approach for Next Generation Thin Film Photovoltaics.” Energy and Environmental Science. (Online Article). DOI: 10.1039/c3ee41627e
- T. Jacobsson, V. Fjallstrom, M. Edoff, T. Edvinsson. (2015, Mar.). “CIGS Based Devices for Solar Hydrogen Production Spanning from PEC-cells to PV-electrolyzers: A Comparison of Efficiency, Stability and Device Topology.” Solar Energy Materials & Solar Cells. (Online Article). DOI: 10.1016/j.solmat.2014.11.041
I would first like to acknowledge the Writing Center for helping me with the development of this paper. I’d also like to thank my writing instructor, Mrs. Liberty Ferda, for being willing to answer any questions I had with this assignment. Finally, I’d like to thank my roommate Jack Fried for keeping me focused and being part of insightful discussions regarding my topic.