The Fritz Haber Institute’s NOMAD Laboratory has been studying how surfaces react to reactive gas phases. This is under various pressure and temperature conditions. The so-called replica exchanging grand canonical method was developed (REGC). The journal published the results. Physical Review LettersOn the 17th of June.
Replica exchange is when many replicas are prepared for the silicon surface and come in contact with different hydrogen atmospheres. These replicas are exchanged during the simulation. The “Grand-canonical”, or silicon surface of each replica, exchanges deuterium molecules or atoms with the deuterium reservoir it touches. Eventually, equilibrium is achieved with the deuterium reservoir.
Understanding the morphology, and structural evolution of material surfaces under a reactive atmosphere is key to understanding the mechanisms of e.g. heterogeneous catalysis reactions and electrocatalysis due to the structure-property-power relationship. The technology is crucial for designing surface properties that can be reasonably designed. This includes the accurate tracking of phase equilibria. The singularities of a reaction functions (e.g. The heat capacity. FHI researchers addressed this challenge with the Replica Exchange Grand Canonical(REGC) method, which is combined with molecular dynamic. This approach captures the surface restructuring under various reactive conditions and also identifies surface phases transition lines, as well as triple- and critical points.
The dissociative absorption of molecular hydrocarbons on the silicon surface is a critical criterion in the research of adsorption systems. This has important applications, such as surface passivation. This REGC approach can be demonstrated by placing a silicon surface in direct contact with a deuterium atmosphere. The REGC approach has identified 25 thermodynamically stable surfaces in temperatures ranging from 300 to 1,000 Kelvin. Many of the identified phases, along with some phase transitions between order or disorder, have not previously been observed experimentally. The dynamic formation or breaking Si-Si bonds can also be responsible for the phase transitions between experimentally confirmed adsorption patterns.
The REGC method combines traditional condensed matter statistical mechanics and state-of the-art electronic structure calculations to predict stability phases of real systems. The approach can also have a significant impact in surface restructuring calculations in surface science. It is possible to apply it to a wide range of important applications, such as heterogeneous and electrocatalysis, surface segregation, and even surface segregation.