Warm dense matter¹ represents an extreme state comprising a matter regime characterized by high temperatures and high pressures. In the warm dense matter regime, electrons are partially degenerate, exhibiting non-negligible quantum effects. Therefore, an adequate quantum-mechanical description of electrons is indispensable. While Kohn-Sham Density Functional Theory (KS-DFT) provides high accuracy, but its computational cost becomes prohibitive at high temperatures as the number of required orbitals increases. Conversely, Orbital-Free DFT (OF-DFT) is computationally efficient but suffers from limited accuracy, particularly in describing inhomogeneous electron systems due to the limit of kinetic energy density functionals and pseudopotential^2,3. By integrating the accuracy of KS-DFT with the efficiency of OF-DFT, we propose a hybrid OF/KS-DFT scheme tailored for warm dense matter simulations. By employing KS orbitals for low-energy states and the OF-DFT method for the higher energy spectrum, our hybrid approach overcomes the intrinsic limitations of OF-DFT while maintaining computational efficiency. Preliminary results demonstrate that this method achieves KS-level accuracy at a significantly reduced cost, offering a promising method for the simulation of large-scale warm dense matter systems.

[1] J. Vorberger, F. Graziani, D. Riley, A. D. Baczewski, I. Baraffe, M. Bethkenhagen, S. Blouin, M. P. Böhme, M. Bonitz, M. Bussmann et al., arXiv:2505.02494 (2025).
[2] C. Ma, M. Chen, Y. Xie, Q. Xu, W. Mi, Y. Wang, and Y. Ma, Phys. Rev. B 110, 085113 (2024).
[3] Q. Xu, C. Ma, W. Mi, Y. Wang, and Y. Ma, WIREs Comput. Mol. Sci. 14, e1724 (2024).
 

Density Functional Theory,Warm Dense Matter,Electronic structure