Flux line pinning by defects in high Tc superconducting crystals

The possibility of flux pinning by different defects in the volume of high-T_c superconductors is investigated. The elementary pinning potential, U_P, and the pinning force, f_P, of point defects (vacancies), one dimensional defects (dislocations), two-dimensional defects (twin and low angle boundaries) and three dimensional defects (pores, precipitates, etc.) are estimated. The effectivity of the different defects acting as pinning centres is examined.