Adsorption energy is defined as the decreasing energy when two materials are combined under the adsorption process in which an atom, ion, or molecule (adsorbate) is attached to the surface of a solid (adsorbent). Adsorption energy is obtained by calculating the difference between the energy of the adsorption model and the sum of the energy which separately calculated for each structure composing the adsorption structure. Adsorption energy, Ea, can be calculated as follows:
Therefore, in order to obtain the adsorption energy, scientists usually calculate the energies for the following three models: Slab supercell structure which is also called adsorbent, adsorption system which is the slab structure with the adsorbent, and adsorbate in the vacuum.
Figure 1. DFT calculations to investigate the catalytic performances of Niphosphide. (a) Optimized surface structures. (b) Free energy profiles. (Loco, D.; et al. 2015)
At Alfa Chemistry, we have developed a mature workflow for calculating the adsorption energy of gas molecules on metal surfaces. Our reliable adsorption energy calculation process is as follows:
At Alfa Chemistry, we provide density functional theory, cluster model and molecular simulation methods to perform accurate adsorption energy calculation. Our fast and high-quality services include the following:
We conduct large-scale DFT calculations to study the interaction between metal particle size and the covering effect of gas molecules.
1. We can study the adsorption of individual gas molecules at several adsorption sites on metal particles of different sizes.
2. Our experts also investigate in detail the influence of different ratios of gas molecule monolayer coverage, and calculate the adsorption energy of each gas atom of metal particles with multiple gas molecule coverage.
3. Moreover, according to the distribution of gas atoms of each metal particle size and the electron changes caused by adsorption on the metal particles, the dependence of the gas coverage of the adsorption energy of each gas atom is analyzed.
Alfa Chemistry supports the calculation of solid surface reaction/adsorption based on quantum mechanics method. Our teams have established a cluster model to solve the surface calculation problems. We can perform calculation of the adsorption energy of gas/liquid molecules physically adsorbed on the metal surface. Our well-designed process is as follows:
(1) Construct the metal clusters
(2) Put the gas/liquid molecules into the metal cluster to get the initial structure of the composite
(3) Optimize the structure of the compound
(4) Calculate the single point energy of each segment
(5) Calculate the difference to obtain the adsorption energy
The adsorption process is usually difficult to observe with experimental methods. Molecular simulation methods are useful tools to simulate the structure and behavior of molecules at the atomic and molecular levels, thereby revealing the mechanism of the adsorption phenomenon. At Alfa Chemistry, we use quantum mechanics method to simulate and study the adsorption of gas on the metal surface.
1. DFT in quantum mechanics combined with the periodic plate model is applied to calculate the vertical adsorption energy and adsorption structure of the gas on the metal surface.
2. The molecular dynamics (MD) method is used to simulate the diffusion of gas molecules on the metal surface, and the cluster analysis method is also applied to calculate the molecular diffusion coefficient.
We use DFT calculations combined with MD simulations to study the adsorption mechanism of gas on solid surfaces in aqueous media.
1. Our scientists use this technique to evaluate global reactivity descriptors such as frontier molecular orbital energy (EHOMO and ELUMO), interstitial energy (ΔEgap), absolute hardness (η) and softening (σ), transferred electron fraction (ΔN) and electronegativity (χ).
2. The dynamic descriptors obtained by MD simulations are also calculated and discussed, such as adsorption energy (Eads), total energy (Etot), deformation energy (Edef), rigid adsorption energy (RAE) and dEads/dNi.
1. Our experts use the significantly increased value of the vacuum layer thickness to repeat the calculation of chemical adsorption energy.
2. A more accurate k-point sampling density is applied to calculate the adsorption energy.
3. We can also enhance the reliability of adsorption energy calculation by adding the energy cutoff calculation.
Our adsorption energy calculation services remarkably reduce the cost, promote further experiments, and enhance the understanding of chemical process for customers worldwide. Our personalized and all-around services will satisfy your innovative study demands. If you are interested in our services, please don't hesitate to contact us. We are glad to cooperate with you and witness your success!