help explaining the physical meaning of these words

[youngjfly]

SingleZeta

SingleZetaPolarized; SingleZeta plus one basis orbital for the first unoccupied shell

DoubleZeta; two basis orbitals for each valence orbital

DoubleZetaPolarized; DoubleZeta plus one basis orbital for the first unoccupied shell

DoubleZetaDoublePolarized



Can someone explain these words to me ?And tell me their difference.
Thank you.

[hkuieagle]

Guy,why don't you ask zhoulp?

[zh]

For these basic concepts, the better way is to read the literature to understand their details:
J. M. Soler, E. Artacho, J. D. Gale, A. García, J. Junquera, P. Ordejón, and D. Sánchez-Portal, J. Phys. Condens. Matter 14, 2745 (2002).
http://iopscience.iop.org/0953-8984/14/11/302/


http://www.shodor.org/chemviz/basis/teachers/background.html
http://books.google.com.sg/books?id=UQAa40eNbmwC&lpg=PA110&ots=kw2I-ugmzj&dq=Single%20Zeta%20atomic%20orbital&pg=PA110#v=onepage&q=Single%20Zeta%20atomic%20orbital&f=false

[youngjfly]

thank you for your good-to-excellent help.