Negative polarizability for H2 at larger r ( freq. dependent )

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ankit7540
Posts: 26
Joined: 05 Sep 2015, 10:49
First name(s): ANKIT
Last name(s): RAJ
Affiliation: National Chiao Tung University
Country: Taiwan, Province of China

Negative polarizability for H2 at larger r ( freq. dependent )

Post by ankit7540 » 28 Jun 2017, 03:56

Dear all,
Hello.
I ran calculation on H2 for frequency dependent polarizability at lower wavelengths ( 120 nm to 151 nm; 0.3796 to 0.3000 hartree).
However as we go to larger inter-nuclear distance the alpha_{zz} is reported to be -ve. However this does not happen for smaller r, and larger wavelengths ( > 200 nm, <0.2750 Hartree). Can somebody suggest how to tackle this.

What I tried to check this : changed the frequency by small units (-0.0001 Hartree ) several times but always alpha_{zz} was found to be -ve near lower wavelengths.

The output file is attached. ( Method : aug-cc-pV6Z, CCSD, tight convergence of energy, H2)
Attachments
pol_ccsd_H2_large_r.out
Output for CCSD H2, freq dep polarizability
(101.93 KiB) Downloaded 78 times
Best regards.
Ankit

kennethruud
Posts: 241
Joined: 27 Aug 2013, 16:42
First name(s): Kenneth
Last name(s): Ruud
Affiliation: UiT The Arctic University of Norway
Country: Norway

Re: Negative polarizability for H2 at larger r ( freq. dependent )

Post by kennethruud » 30 Jun 2017, 13:44

Dear Ankit,

I believe this is a correct result and a consequence of the fact that the lowest excited state in the totally symmetric irrep becomes lower as you stretch the bond. The polarizability will change sign once you pass the lowest excited state of a given symmetry, as shown for instance by Norman and coworkers (http://aip.scitation.org/doi/pdf/10.1063/1.2107627, figure 1 on page 17 on this manuscript).


Best regards,

Kenneth

ankit7540
Posts: 26
Joined: 05 Sep 2015, 10:49
First name(s): ANKIT
Last name(s): RAJ
Affiliation: National Chiao Tung University
Country: Taiwan, Province of China

Re: Negative polarizability for H2 at larger r ( freq. dependent )

Post by ankit7540 » 01 Jul 2017, 06:55

Dear Kenneth Ruud,
Thank you very much for the manuscript.
Best regards.
Ankit

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