Double-zeta Slater-type basis sets with noninteger principal quantum numbers and common exponents

A double-zeta basis set of extended Slater-type functions, whose principal quantum numbers are allowed to have noninteger values, is reported for the atoms He to Ar in their ground state. The total energies are lower than those from conventional and improved double-zeta basis sets, in which the principal quantum numbers are restricted to integer values. For the same atoms, we develop a new type of double-zeta basis set that combines the use of noninteger principal quantum numbers and the use of common exponents in Slater-type functions. The new double-zeta basis sets result in an improvement of the energy and a reduction of the computational time.