An international collaboration with colleagues from over 30 universities and institutes to investigated to what extent quantum simulations of material properties agree when they are performed by different researchers and with different software. Thanks to an online collaboration, they successfully demonstrated that the most recent generations of codes agree well, in contrast to earlier generations. Their study appeared in week’s edition of Science.
Reproducibility does not come easily
It’s a corner stone of science: independent yet identical experiments should produce identical results. Only in this way can science identify ‘laws’, which lead to new insight and new technologies. However, several recent studies have pointed out that such reproducibility does not always come spontaneously. In scientific areas as diverse as psychology research and genetic research, cases were identified where repeating previous experiments led to very different results. Even predictions by computer codes require caution, since the way in which theoretical models are implemented may affect simulation results. This is a reason for concern in any field of research that critically depends on computer simulations. For the study and design of materials, for instance, there are several independent software packages available based on quantum physics. They are moreover being used increasingly often in automated procedures with limited human supervision. It is therefore essential to know to what extent predicted materials properties depend on the code that has been used.
Online collaboration brings experts together
Despite the need for reliable property predictions of materials, the reproducibility of quantum simulations had not been investigated systematically before. This is mainly because there is no single person sufficiently skilled in all existing codes. Scientists from the University of Basel and Max-Planck Institute for Micstructructure Physics therefore joined forces with more than 60 colleagues, bringing together the know-how of over 30 prominent institutions. The researchers investigated 40 different methods to describe the influence of pressure in 71 different crystals. Among these methods was the ELK, Abnit and BigDFT codes. The team can now demonstrate that, although a few of the older methods clearly yield deviating results, predictions by recent codes are entirely equivalent. They moreover define a quality criterion that allows the verification of future software developments against their extensive database. New test data are continuously added to a publicly available website (http://molmod.ugent.be/DeltaCodesDFT).
The researchers involved hope that their work will contribute to higher standards for materials property simulations, and that it will facilitate the development of improved simulation codes and methods: essential for the intelligent design of novel materials to address society’s challenges in the 21st Century.
I have had the great opportunity to be part of this work “Reproducibility in density functional theory calculations of solids” which is now published in Science. If you need access to the paper do not hesitate.