I. P. Koutsaroff (1) ,* , C. Moe (1b), Dae Ho Kim (1), K. Cheema(1), and Garrett M. Tow (2)

1. Akoustis Technologies Corp., 858 FM 1209 Bastrop, TX 78602 USA
1b Akoustis Technologies Corp., 5450 Campus Drive, Canandaigua, NY 14424 USA

2.  Materials Design Inc., 12121 Scripps Summit Drive, Suite 160, San Diego, CA 92131 USA

*Corresponding Author: ikoutsaroff@akoustis.com

In the present study, we adopt a comprehensive approach of ab-initio simulations by using a commercial software package VASP 6.5.1 based on Density Functional Theory (DFT) using a projector augmented wave (PAW) method with generalized gradient approximation (GGA) along with Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and calculations are performed on a grid of points in real space, which allowed us to calculate the full set of piezoelectric and mechanical (acoustic) properties of Al1−xScxN (0≤x≤0.5, AlScN) and Al1−xBxN (0≤x≤0.5, AlBN) at 0K, as well as from 200K to 500K [1, 2]. The measured phase velocities and piezoelectric coupling coefficients, kt2 from Al1−xScxN (0.31≤x≤0.38, AlScN) based Thin Film Bulk Acoustic Wave Devices at 5-7 GHz allowed good consistency when comparing with ab-initio simulated piezoelectric and stiffness tensors. Two-layer Graph Atomic Cluster Expansion (GRACE-2L) Universal Machine Learning Interatomic Potential (uMLIP) ) trained on the Meta Open Materials 2024 (OMat24) dataset, was utilized in predicting e33, k2, C33 and lattice densities from 200K to 500K temperature range for Al1−xBxN (0≤x≤0.5, AlBN).

References

[1] O. Ambacher,  et al., Wurtzite ScAlN, InAlN, and GaAlN crystals, a comparison of structural, elastic, dielectric, and piezoelectric properties, J. Appl. Phys. 28 July 2021; 130 (4): 045102 https://doi.org/10.1063/5.0048647.

[2] I.P., Koutsaroff, et al., High Accuracy Elastic and Piezoelectric Properties Predictions of Al1−xScxN Materials and their Experimental Validation from Microacoustic Resonators within 2.7-5.1 GHz range, Joint ISAF-ICE-EMF-IWPM-PFM Meeting (ISAF 2019) July 14-19, 2019, Lausanne, Switzerland.

[3] I.P., Koutsaroff, et al., Ab-initio Modeling of Wurtzite AIBScN and Characterization of AIBScN Piezoelectric thin Film Surface Acoustic Wave Devices Covering 4-8 GHz, The Materials Design MedeA User Group Meeting (UGM 2025), October 6-8, 2025, Vienna, Austria.