A new metastable phase for shock compressed Copper

Copper is utilized in many different applications within the shock compression community (such as pistons in NIF) primarily because it is believed that it does not undergo any solid-solid phase transition prior to melting. However, studies have demonstarted coordination number loss behind shock front. A recent MD study by the authors group demonstrated that solid-solid phase transition occurs in Cu under shock compression to that of the BCT phase [1]. However, any MD calculations are dependent on the interatomic force potentials used, which for the previous study was taken as EAM-Mishin potential for Cu having valence shell containing “s” orbitals. To rule out any forcefield issues, DFT studies were carried out. DFT studies are for 0K temperature, whereas under shock compression there is a significant rise in temperature for Cu samples. Thereby, Gibbs free energy calculation within the quasiharmonic approximation is carried out to demonstrate the feasibility of existence of BCT phase for Cu shock compressed along 001 direction [2], supporting previous postulation by Friedel.
Ref.
[1] Neogi, A., and Mitra, N. (2017). Scientific Reports. 7, 7337.
[2] Dey, U., Mitra, N., and Taraphder, A. (2019). Computational Materials Science, 170, 109154.