Computational Physics Studies: From Atomic Fine-structure To Crystal Equation Of State

From atomic fine-structure to crystal equation of state, we elucidated four physics problems by the computational methods.Using a simplified multi-configuration Dirac-Fock (SMCDF) scheme, we studied the systematic variations of the fine-structure splittings of n2D3/2,5/2 Rydberg series along the sodium-like isoelectronic sequence. The major mechanism, i.e. the competition between"the spin-orbit interactions"and"the exchange interactions due to relativistic effects of the nd orbital wave functions", well explained such variations. Furthermore, the effect of Breit interactions which plays the secondary role is studied.The accurate atomic data of Nitrogen and Nitrogen-like ions are relevant to fusion plasma studies and astrophysics studies. The precision calculation of fine-structures is required to obtain such atomic data. Along the whole Nitrogen isoelectronic sequence, the contributions of the electron correlations, the Breit interactions and the quantum electrodynamics corrections on the ground-state fine-structures are elucidated. Furthermore, we elucidated the mechanism of the abnormal fine-structure orderings under L-S coupling. With the great developments of computation science and technology, we are able to study the recombination processes of H+2, HD+ and D+2 with high-energy electrons based on a time-dependent wave packet dynamics method. The final vibrational distributions of the products (H2, HD and D2) have been studied. The isotope effects of the final vibrational distributions and their dependence on initial states are elucidated.In order to calculate equation of state (EOS) at 0 K for copper properly, the high pressure part of EOS is calculated based on the first-principles all-electron full-potential augmented-plane-wave plus local orbital (APW+lo) method, and the low pressure part is calculated by the Murnaghan equation with experimental parameters. The two parts of the recommend EOS are connected by cubic spline interpolations. Our recommend EOS from -2GPa to 10000GPa is in good agreement with the available experimental data. Furthermore, the agreement between theoretical EOS of hcp and fcc lattices at extremely compressed condition sets the foundation of spherical atom models for high density and high temperate plasmas.