Does scaling or addition provide the correct frequency dependence of β(-ωσ; ω1, ω2) at the correlated level? An investigation for six molecules

Erik K. Dalskov*, Hans Jørgen Aa Jensen, Jens Oddershede

*Kontaktforfatter for dette arbejde

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Resumé

The frequency dependent polarizability α(-ωσ; ω1) and the frequency dependent first hyperpolarizability β(-ωσ; ω1, ω2) have been calculated using both self consistent field (SCF) and multiconfigurational SCF (MCSCF) linear and quadratic response functions for six small molecules: BH, CO, HF, H2O, NH3, and H2S. Two approximate ways of using the calculated dispersion at the SCF level to describe the frequency dependence at the correlated level, referred to as scaling and addition, have been tested. Calculated frequency dependent MCSCF results are used to investigate the validity of these approximations. Our results indicate that, if the correlation correction to the static average hyperpolarizability is large, then the approximations do not hold. The same conclusion holds if correlation changes the sign of the average first hyperpolarizability at zero frequency. There is also a tendency towards an underestimation of the frequency dependence if scaling or addition is applied. There does not seem to be a simple way to infer anything about the validity of scaling or addition for β from either the lower lying excitations and their intensities or from the frequency dependence of the dipole polarizability.

OriginalsprogEngelsk
TidsskriftMolecular Physics
Vol/bind90
Udgave nummer1
Sider (fra-til)3-14
Antal sider12
ISSN0026-8976
StatusUdgivet - jan. 1997

Fingeraftryk

Carbon Monoxide
scaling
Molecules
self consistent fields
molecules
approximation
tendencies
dipoles
excitation

Citer dette

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title = "Does scaling or addition provide the correct frequency dependence of β∥(-ωσ; ω1, ω2) at the correlated level? An investigation for six molecules",
abstract = "The frequency dependent polarizability α(-ωσ; ω1) and the frequency dependent first hyperpolarizability β(-ωσ; ω1, ω2) have been calculated using both self consistent field (SCF) and multiconfigurational SCF (MCSCF) linear and quadratic response functions for six small molecules: BH, CO, HF, H2O, NH3, and H2S. Two approximate ways of using the calculated dispersion at the SCF level to describe the frequency dependence at the correlated level, referred to as scaling and addition, have been tested. Calculated frequency dependent MCSCF results are used to investigate the validity of these approximations. Our results indicate that, if the correlation correction to the static average hyperpolarizability is large, then the approximations do not hold. The same conclusion holds if correlation changes the sign of the average first hyperpolarizability at zero frequency. There is also a tendency towards an underestimation of the frequency dependence if scaling or addition is applied. There does not seem to be a simple way to infer anything about the validity of scaling or addition for β∥ from either the lower lying excitations and their intensities or from the frequency dependence of the dipole polarizability.",
author = "Dalskov, {Erik K.} and Jensen, {Hans J{\o}rgen Aa} and Jens Oddershede",
year = "1997",
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language = "English",
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pages = "3--14",
journal = "Molecular Physics",
issn = "0026-8976",
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Does scaling or addition provide the correct frequency dependence of β(-ωσ; ω1, ω2) at the correlated level? An investigation for six molecules. / Dalskov, Erik K.; Jensen, Hans Jørgen Aa; Oddershede, Jens.

I: Molecular Physics, Bind 90, Nr. 1, 01.1997, s. 3-14.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

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AU - Dalskov, Erik K.

AU - Jensen, Hans Jørgen Aa

AU - Oddershede, Jens

PY - 1997/1

Y1 - 1997/1

N2 - The frequency dependent polarizability α(-ωσ; ω1) and the frequency dependent first hyperpolarizability β(-ωσ; ω1, ω2) have been calculated using both self consistent field (SCF) and multiconfigurational SCF (MCSCF) linear and quadratic response functions for six small molecules: BH, CO, HF, H2O, NH3, and H2S. Two approximate ways of using the calculated dispersion at the SCF level to describe the frequency dependence at the correlated level, referred to as scaling and addition, have been tested. Calculated frequency dependent MCSCF results are used to investigate the validity of these approximations. Our results indicate that, if the correlation correction to the static average hyperpolarizability is large, then the approximations do not hold. The same conclusion holds if correlation changes the sign of the average first hyperpolarizability at zero frequency. There is also a tendency towards an underestimation of the frequency dependence if scaling or addition is applied. There does not seem to be a simple way to infer anything about the validity of scaling or addition for β∥ from either the lower lying excitations and their intensities or from the frequency dependence of the dipole polarizability.

AB - The frequency dependent polarizability α(-ωσ; ω1) and the frequency dependent first hyperpolarizability β(-ωσ; ω1, ω2) have been calculated using both self consistent field (SCF) and multiconfigurational SCF (MCSCF) linear and quadratic response functions for six small molecules: BH, CO, HF, H2O, NH3, and H2S. Two approximate ways of using the calculated dispersion at the SCF level to describe the frequency dependence at the correlated level, referred to as scaling and addition, have been tested. Calculated frequency dependent MCSCF results are used to investigate the validity of these approximations. Our results indicate that, if the correlation correction to the static average hyperpolarizability is large, then the approximations do not hold. The same conclusion holds if correlation changes the sign of the average first hyperpolarizability at zero frequency. There is also a tendency towards an underestimation of the frequency dependence if scaling or addition is applied. There does not seem to be a simple way to infer anything about the validity of scaling or addition for β∥ from either the lower lying excitations and their intensities or from the frequency dependence of the dipole polarizability.

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