Subject: EH parameters for solids

From: <[email-masked]>
Date: Tue Mar 15 20:04:21 1994

Dear Netters!
            Presently, we are attempting to determine the
electronic structure (band structure, DOS, COOP, etc) of
solid state compounds syntetized and characterized in our
laboratory (MCuFeX2, M=Li,Na,K,Cs,Rb and X=S,Se,Te) using
extended Huckel tight-binding method (EHMACC package)
           However, we have several doubts about the way
of choosing orbital parameters (Hii, Slater exponents).
We has nearly reproduced the band structure of (Mn2P2)-2
determined by Dr. R. Hoffmann ("Solids and Surfaces,
R. Hoffmann, VCH Publishers, 1988, p.60), using the
orbital parameters of Mn given in the Alvarez's Tables:
    Hss = -7.5      exp s = 1.80
    Hpp = -3.8      exp p = 1.80
    Hdd = -8.7      exp d1 = 5.15    c1 = 0.514
                    exp d2 = 1.70    c2 = 0.693
        However, we attempted to improve our results using
the orbital parameters given by Kematics and Myers for the
Mn in a MnAl alloy (Inorg.Chem, (1992), p.3568-3572), but
the band structure obtained has no similarity with the
Hoffmann's band structure for the (Mn2P2)-2.
       Our question  are the following:
-What are the criteria for choosing the orbital parameters
for elements in a EH-tight-binding calculation?
       If someone have any insinuation or comments about
possible orbital parameters for our solid state compounds,
you are welcome to give us.
      A last thing. I'm intrigued because this list are
dominated by the molecular quantum chemist and almost no
posting about solid state quantum chemistry.
     In advence, I appreciate and thank for your comments
and helps.
            ANTONIO BULJAN H
            Dept. of Chemistry
            Universidad Catolica del Norte
            [email-masked]
            [email-masked]