Subject: great deviation of calculated polarizability from observed polarizability

From: Pang Siu Kwong <[email-masked]>
Date: Sat, 31 Jan 1998 13:57:44 +0800 (HKT)

Hello!  Is there any difference between the polarizability calculated by 
MP2 and DFT(BP86), and observed polarizability from databook?  
For example, the Gaussian 94 and basis set is 6-311G(d,P) are used, and the 
polarizability of water molecule calculated by MP2 and DFT(BP86) are :

MP2 
alpha(XX) = 3.994 bohr^3
alpha(YY) = 7.498 bohr^3
alpha(ZZ) = 5.704 bohr^3
static polarizability = 5.732 bohr^3 (8.5E-31 m^3)

DFT(BP86)
alpha(XX) = 4.168 bohr^3
alpha(YY) = 7.789 bohr^3
alpha(ZZ) = 6.021 bohr^3
static polarizability = 5.999 bohr^3 (8.9E-31 m^3)

Geometry (CRC Handbook)
bond length OH = 0.958
bond angle HOH = 104.45

Observed polarizability of water = 1.48E-24 cm^3, 1.48E-30 m^3 (P.W. Atkins, 
Table of data in Physical Chemistry, 3rd edition, Oxford University Press)

Why there is a great deviation of calculated polarizability from 
observed polarizability?

Patrick Pang