An international team of scientists has developed the VelCrys application, which enables the calculation and visualisation of acoustic wave propagation in crystals, as well as the influence of magnetic fields on their velocity. The tool may support the development of new sensors, magnetoacoustic materials, and ultrasound technologies. Experts from IT4Innovations National Supercomputing Center at VSB – Technical University of Ostrava were involved in the application development.
When sound propagates through ordinary media such as air or water, its properties can be described relatively simply. In crystals, however, the situation is considerably more complex. Their internal structure causes acoustic waves to travel at different speeds in different directions. This phenomenon, known as anisotropy, plays an important role in fields such as geophysics, materials research, and the development of biosensors.
An international team of scientists from the Czech Republic and Spain has focused on this problem and developed the open-source software VelCrys. The programme can calculate the speed of acoustic waves in crystals and display it using three-dimensional maps. It also allows users to simulate how the propagation of sound is affected by an external magnetic field. In its development, the authors used analytical models for calculating sound propagation in anisotropic materials and combined them with the theory of magnetoelastic phenomena, i.e. the interaction between magnetism and mechanical deformation of materials.
In crystals, three basic types of acoustic waves arise – one quasi-compressional and two quasi-shear waves. Each of them can propagate at a different speed depending on the crystal’s orientation. VelCrys therefore generates three-dimensional “velocity maps” that show how the speed of sound changes with the direction of propagation.
One of the programme’s key functions is the simulation of the influence of a magnetic field on sound propagation in magnetostrictive materials. These are materials that change their mechanical properties or dimensions when exposed to a magnetic field. This phenomenon was first described in 1958 and is often referred to as the Simon effect. VelCrys makes it possible to calculate these changes for different wave propagation directions as well as orientations of the magnetic field.
The functionality of the programme was validated by researchers from the University of Oviedo, the Catalan Institute of Nanoscience and Nanotechnology, and IT4Innovations National Supercomputing Center, namely Dominik Legut and Ievgeniia Korniienko from the Laboratory for Modelling for Nanotechnologies, on several materials. One of them was dry sandstone, for which VelCrys reproduced previously published results on the propagation of acoustic waves. Another example was an alloy of cobalt and platinum used in magnetic applications and nanotechnologies. Here, the simulation results matched experimental measurements as well as theoretical models. The researchers also tested cobalt with hexagonal symmetry, where the programme captured changes in wave velocity related to the presence of a magnetic field.
VelCrys is available both as a web application and as an open-source Python module. The software uses the Dash framework, the Plotly library for 3D visualisation, and the NumPy library for certain numerical calculations. The authors expect the tool to find applications in the development of acoustic sensors, magnetic memory devices, and devices based on surface acoustic waves.
The research team is developing the programme to extend support to additional types of crystal symmetries and more advanced magnetic corrections. The first version of VelCrys was published in the scientific journal SoftwareX by Elsevier.
Research article
VelCrys: Interactive web-based application to compute acoustic wave velocity in crystals and its magnetic corrections
https://doi.org/10.1016/j.softx.2025.102472
Image*: Visualisation of changes in the propagation speed of three types of acoustic waves (quasi-compressional qP and two quasi-shear waves – qS1 and qS2) depending on the direction of propagation under the influence of a magnetic field in a cubic crystal of a cobalt–platinum alloy. Created using the VelCrys programme.
* Image from the article: Nieves, P., Korniienko, I., Fraile, A., Fernández-Díaz, J. M., Iglesias, R., & Legut, D. (2026). VelCrys: Interactive web-based application to compute acoustic wave velocity in crystals and its magnetic corrections. SoftwareX, 33, 102472. https://doi.org/10.1016/j.softx.2025.102472, Fig. 5.