Computer simulations improve atom experiments
It is extremely difficult to conduct experiments with atoms, so many scientists use computer simulations, before they perform actual experiments in the laboratory. At a recent Danish quantum science conference, Danish and international scientists presented some of the newest methods in computer simulations with atoms.
What happens to an atom if it is subjected to extreme heat or pressure? It can be difficult to show this in an experiment, but by using computer simulations scientists can see what happens to the small building blocks of the universe under different conditions.
Imagine, for example, that you wanted to further develop a material that can be used to conduct electricity in a mobile telephone. To avoid carrying out large experiments on all possible atoms, you use computer simulation. The computer selects potential atom types, in the material, for you. This means that you only need conduct a few experiments, instead of a whole range.
It was precisely this method that the Belgian scientist Gian-Marco Riagnese presented at the Danish quantum science conference QuantumHagen, held in July 2014, in collaboration between the Technical University of Denmark (DTU) and Quantumwise.
"It takes a long time to carry out experiments, but with computer simulations you can save both time and money," says Anders Blom, customer director at Quantumwise.
When you work with atoms, you are working with a unit of measurement called nanometre (nm).
One nanometre equals one billionth of a metre. A hydrogen atom measures 0.1 nm.
Nanometre is used to describe light. For example, light is visible to us when it has a wavelength of 400-800 nm. Source: Wikipedia
"There's a need for computer simulations, because electronic items, such as mobile phones, are getting smaller and smaller. This means that we need to understand how the individual atoms can perform, and we can do that using computer simulation."
State of the art
Riagnese's project, along with many others, were presented at QuantumHagen. Here, researchers from five continents could hear about recent developments in computer simulation with atoms. They could also get hands-on experience with the Danish-developed programs Virtual NanoLab and Atomistix Toolkit, which can build and simulate atomic structures.
"The good thing about this conference is that we have a common starting point in the methodology, and we can see, how far we can progress in our relevant fields," says Tejs Vegge, who is a professor at DTU's Department of Energy Conversion and Storage. "In this way we get even better. What's being presented here is 'state of the art'."
Computer simulation saves time and money
The tiny atoms of our universe have been a source of amazement since ancient times. Today, we know a great deal about them, but that knowledge hasn't made it any less difficult to carry out experiments with them. Therefore, it is often easier to simulate them using a computer program, where the objective is, for instance, to find out how two types of atoms react with each other if they are under high pressure.
Quantum physics covers almost all aspects of physics and provides a thorough description of atoms, molecules and solid matter.
This field of science is closely connected with Copenhagen and the Niels Bohr Institute, which originated in the Danish physicist Niels Bohr's development of his pioneering atomic model from 1913.
Source: The Niels Bohr Institute
The Danish company Quantumwise developed the two products that were tested at the conference. It may sound quite simple for scientists to use computer programs to simulate atoms, but it often requires a super-computer that is 100 times more powerful than an ordinary laptop if the result is to be precise.
"The simulations are reasonably precise," says Kurt Stokbro, Quantumwise's chief executive officer. "But one of the large problems is that super-computers sometimes spend weeks at a time calculating. We are looking at whether it's possible to make simpler models and better algorithms, so we can reduce the time needed for the calculations."
Atoms can be combined in many ways
For instance, the two programs Virtual NanoLab and Atomistix Toolkit can be used to build materials atom by atom and expose them to high temperatures and pressures. In this way, it is easy for scientists to see which atoms or materials are useable in tomorrow's electronic products.
"The programs can be used to develop new materials for use in electronic items such as mobile telephones and laptops," says Blom. “Also, in another field, they can be used to develop new medicines”.
Tejs Vegge is one of the scientists, who uses Quantumwise's products. He is interested in what happens when different atoms meet and react.
"If we are to combine different atoms or materials, we can do that in many, many ways," says Vegge. "What Atomistix Toolkit does for us is calculate quickly, how they bond to each other in the best way, and what this means for moving electrons, for example. That's extremely difficult to simulate, but their program can do it."
Vegge is currently working on converting nitrogen to ammonia; by using computer simulations, he can study, which nano-particles are best at converting nitrogen to ammonia by using electricity from e.g. wind turbines.
New people – new ideas
For some people, computer simulation with atoms is nerdy and a very male-dominated subject. Most of the people at the conference, were also men – but three women had sneaked in to hear the latest developments in the field.
"Up to now I think it has been very interesting," says one of the three women, Noora Tuomisto, a PhD student at Aalto University in Finland. "Meeting new researchers in your own field is always a good thing, as we can exchange ideas that you may use later in your own work”.