A NEW EMPIRICAL FORMULA FOR CALCULATING THE TRANSITION TEMPERATURES OF A-15 SUPERCONDUCTORS

A new empirical formula for calculating the Tc, of A-15 supereonductors is presented and it reads: Tc=N TA/M1/2(rA/rB) (e/a), where Nnumber of atoms,N = 4 for A3B compounds; TA the superconductive transition temperature of the A element; Mthe. average atomic weight of the compounds; (rA/rB) theatomic radius ratio of elements A and B; (e/a) the eleetron concentration (electrens/atoms). Using the new empirical formula, the supereonductive transition temperatures of A-15 compounds have been calculated, and the results are shown in table 1. As shown in the table the calculated results are much closer to the experimental results than those obtained by other empirical formulas. The highest Tc value of A-15 structural materials may be not higher than 25K.