A time machine to the most stable state
Villigen, 31.03.2026 — GEMS is an open-source software platform that makes chemical and thermodynamic processes in complex systems computable – processes that take thousands of years in nature can be simulated in seconds. A new national consortium will ensure that the software created at PSI is developed and maintained in the long term and jointly funded.
What do a Martian meteorite from the early Solar System, climate-friendly cement and lithium extracted from deep geothermal water have in common? All these systems can be modelled using the same software: GEMS.
GEMS stands for Gibbs Energy Minimisation Software. It was created at PSI more than thirty years ago and has been continuously refined there ever since. Today, this open-source application is used by researchers in Switzerland and around the world; thousands of scientific publications from a wide range of disciplines are based on its calculations and the corresponding databases. A newly founded national consortium – bringing together researchers from PSI, ETH Zurich, Empa, the University of Bern, EPFL and Nagra – will now ensure that the software continues to be developed, maintained and jointly funded in the future.
Martian meteorite, green cement and lithium from deep geothermal water
At first glance, they seem unrelated, but ultimately they are governed by the same chemical principle – Gibbs energy. The concept may appear somewhat abstract, but it is a fundamental quantity in thermodynamics. George-Dan Miron from the PSI Center for Nuclear Engineering and Sciences, who initiated the consortium and is a long-time developer of GEMS, explains the thermodynamic concept using a simple everyday analogy: “Gibbs energy is like a pricing system. Everything in nature follows it – gases, liquids and solids. As soon as they interact, their ‘prices’ start to shift. The state with the lowest ‘price’ is the most stable – and that’s exactly what we want to calculate using GEMS.”
Essentially, it is about understanding how chemical elements are distributed between different phases when a system reaches thermodynamic equilibrium – the state with the lowest ‘price’ – and which parameters determine that final state. For example, researchers at the University of Bern discovered a mineral in a Martian meteorite that had never been seen before in nature. They used GEMS to reconstruct the conditions under which this exotic phase would have formed in the hot, gas-rich environment of the early Solar System. Like a virtual time machine, GEMS allowed them to reconstruct the temperature and pressure conditions that led to the formation of this mineral all that time ago.
GEMS is also central to developing new low-CO₂ cement formulations, such as those being researched at PSI, Empa and EPFL. The software simulates which mineral phases form when the cement hardens, how stable they are and how the material will interact with its environment. This allows researchers to explore hundreds of formulations virtually before mixing a single one in the laboratory – a tremendous advantage in an industry responsible for around eight percent of global CO₂ emissions, where every more climate-friendly formulation counts.
Another example of its application is lithium: this light metal is found in nearly all modern batteries but is mainly extracted in Australia and Latin America – sometimes using methods criticised for their high water consumption. In Switzerland and Europe, intensive research is being conducted into extracting lithium and other rare elements from hot deep geothermal water. Researchers at the University of Bern are planning a new study that will use GEMS to calculate how the chemical composition of these fluids changes under different conditions and to identify processes that could enable the selective extraction of lithium.
GEMS is one of a kind
These three examples demonstrate the wide variety of applications for which GEMS is used today – ranging from planetary science to cement research and geochemistry. However, the software was devised at PSI for a very specific task: understanding how the materials in a deep geological repository change over tens to hundreds of thousands of years. Researchers working on the Swiss deep-repository project needed to understand how steel, concrete, water and rock interact chemically – and how these interactions evolve over vast geological timescales.
When powerful personal computers began to make their way into research in the late 1980s, the geochemist Dmitrii Kulik began to systematically develop the prototype of a geochemical modelling tool at PSI. He structured the initial work, refined the underlying concept, and, with the assistance of his colleagues, built GEMS to become a powerful thermodynamic modelling platform that grew rapidly and became increasingly capable.
At the same time, PSI researchers were working in close collaboration with the National Cooperative for the Disposal of Radioactive Waste (Nagra), conducting numerous experiments, some of them in the PSI Hot Laboratory. Here, they investigated how radionuclides interact with natural rocks, such as Opalinus Clay, as well as with concrete and other materials, how they migrate through them, and which new mineral phases are formed in the process. Every experiment provides additional input for GEMS-based modelling, making it possible to accurately simulate processes across a range of conditions that are relevant to deep geological repositories.
Over the years, this has produced a substantial body of experimental data, comprehensive thermodynamic databases and a large suite of models that – taken together – make GEMS truly unique in the world.
Consortium for the future of GEMS
The success story of GEMS has also faced some challenges: with every new application, every published study and every additional model, the effort required to maintain, modernise and keep the software up to date increases.
The newly established national consortium, created by the participating institutions, provides a framework for sharing this responsibility and jointly supporting the further development, maintenance and funding of the software. Following the retirement of Dmitrii Kulik, George-Dan Miron has taken over as scientific lead of the project: “GEMS should remain a state-of-the-art open-source software platform, supporting researchers worldwide across disciplinary boundaries and continuing to evolve.”
Text: Paul Scherrer Institute PSI/Benjamin A. Senn
Contact
Dr. George-Dan Miron
PSI Center for Nuclear Engineering and Sciences
Paul Scherrer Institute PSI
+41 56 310 24 32
dan.miron@psi.ch
[English]