NOTE ON THE CHOICE OF BASIS-SET IN DENSITY-FUNCTIONAL THEORY CALCULATIONS FOR ELECTRONIC-STRUCTURES OF MOLECULES (TEST ON THE ATOMS FROM THE FIRST 3 ROWS OF THE PERIODIC-TABLE (2-LESS-THAN-OR-EQUAL-TO-N-LESS-THAN-OR-EQUAL-TO-Z-LESS-THAN-OR-EQUAL-TO-18), WATER, AMMONIA AND PYRROLE)

The effect of basis set in Kohn-Sham theory on estimating correlation energy was investigated using a density functional subroutine and a Hartree-Fock SCF one-electron density program (working with arbitrary basis set). Lee-Yang-Parr density functional estimation, MP2 perturbation calculation and Davidson's accurate configuration interactions calculations for correlation energies of atoms were used for this test. In the density functional estimation a simple 3-21G basis set has produced the same results as the huge triple-zeta basis set with polarization functions within the chemical accuracy (1 kcal/mol).