# A Calculation Method for Surface Energies with Thermodynamic Characteristics and Its Application in Investigating Activity Mechanisms for Nanoporous W

## TL;DR

This paper introduces a new method to calculate surface energies in thermodynamically suitable units and applies it to study nanoporous tungsten activity.

## Contribution

A novel computational method converts surface energy units to kJ/mol and determines surface layer thickness for thermodynamic analysis.

## Key findings

- Surface energy values in kJ/mol are more suitable for thermodynamic analysis than J/m².
- The extended Finnis Sinclair potential helps determine the appropriate surface layer thickness (t₀).
- Nano-treatment analysis confirms the validity of the new method and explains nanoporous W activity.

## Abstract

Surface energy is involved in various thermodynamic processes, providing a driving force for thermodynamic reactions. However, surface energies applied in current engineering calculations are generally measured in J/m2, which is unsuitable for thermodynamic analysis. To solve this problem, the calculation formula for surface energies was modified to convert the unit of measurement, transforming the non-thermodynamic measurement unit J/m2 into the thermodynamically characterized kJ/mol. The calculated surface energy values measured in kJ/mol are unstable due to the influence of the number of atomic layers (t) in the constructed models. Meanwhile, the problem of determining the surface layer thickness, i.e., the number of atomic layers with surface characteristics (t0), remains unresolved in surface science. Therefore, the extended Finnis Sinclair (EFS) potential was improved by extending the nearest neighbor range and utilized in analyzing the energy per atom, resulting in the determined number of t0. These results suggest that selecting the surface layer number corresponding to the first to third nearest-neighbor atoms could be appropriate, and the resulting surface energies in kJ/mol appear reasonable. The validity of this computational method and the origin of nanoporous W activity were confirmed by analyzing the changes in total surface energy before and after nano-treatment using the novel nanosized approach.