Subject: hyperpolarizabilities results in G98

From: "Sahan Thanthiriwatte" <[email-masked]>
Date: Sun, 25 Mar 2001 10:58:02 +0600

Dear Sir,

	I got to know your address from CCL.NET web site while I was searching WWW 
under hyperpolarizability. I am sure that information, which I need about 
hyperpolarizability is with you.

	I am an undergraduate in University of Colombo, Sri Lanka, following 4 
years special degree in chemistry. I am in 4th year and highly involve in my 
research project for the partial fulfillment of my degree. I am very fond of 
theoretical chemistry so I choose that area for my research project. 
According to my project I investigate polarizability (alpha) and second 
order polarizability, called hyperpolarizability (beta). While continuing my 
project work, recently my university purchased Gaussian 98W from Gaussian, 
Inc., USA. I use Gaussian to optimize molecular structures and to calculate 
polarizability and hyperpolarizability for observe non-linear molecular 
properties.

	I use Pentium® P-III 550MHz PC with windows™ 98 environment.

	As I found 6-21G(d) basis set and HF Ab initio method are best way to 
calculate polarizability and hyperpolarizability.

	Initially I optimize molecular structure at the Hartree-Fock level by using 
the following line: #T HF/6-31G(d) OPT=Z-MATRIX. After that when molecule 
optimize I calculate polarizability and hyperpolarizability using optimized 
final z-matrix as an input (*.GJF) using the following line: #P HF/6-31G(d) 
POLAR.

Gaussian 98 User’s reference says (P155) polarizability and 
hyperpolarizability can calculate at HF and all DFT methods. Also the book 
“Exploring Chemistry with Electronic Structural Methods” says (under 
polarizability and hyperpolarizability) #P --/----- POLAR gives 6 values for 
polarizability and 10 values for hyperpolarizability. Also it says those 
value belongs to lower tetrahedral format of both tensors respectively. Also 
#T --/----- POLAR gives Exact polarizability and Approx polarizability. 
Those values have 6 values respectively.
Gaussian gives following values:

Exact polarizability: 283.302   7.400 170.081   0.053   0.214  41.005

Approx polarizability: 208.051   8.157 187.463   0.070   0.192  41.585

And

Polar = 218.7884922,-0.585717,41.007516,-56.5442676,
-0.30562,234.5909358

HyperPolar = 266.1950616,2.051367,4.6963645,0.0314151,-302.0066529,
-0.7294357,-4.9533196,398.6958046,-1.2723125,-693.674482

Following are the some of my problems which was arisen before me while 
continuing project work.

1.) What is meant by “Lower Tetrahedral Format”?

2.) What is the meaning of those 6 and 10 values, given by Gaussian?

3.) Gaussian gives10 values as the output of hyperpolarizability. What are 
the relevant places to those 10 values in hyperpolarizability tensor?

4.) Using those 10 values, How we calculate proper single value for 
represents hyperpolarizability?

5.) What is the meaning of exact polarizability and Approx polarizability 
and how it related to polarizability or hyper polarizability?

6.) Why Gaussian is such slow?

7.) Please let me know, if there are any references and journals regarding 
to my matter.

I shall be very grateful, if you make me aware about above information and 
it will be a great help to complete my research project successfully. Hope 
to hear from you in the near future.

Thank you,
Sahan.

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