In:
Physical Chemistry Chemical Physics, Royal Society of Chemistry (RSC), Vol. 24, No. 32 ( 2022), p. 19463-19472
Abstract:
The molecular first hyperpolarizability β contributes to second-order optical non-linear signals collected from molecular liquids. For the Second Harmonic Generation (SHG) response, the first hyperpolarizability β (2 ω , ω , ω ) often depends on the molecular electrostatic environment. This is especially true for water, due to its large second hyperpolarizability γ (2 ω , ω , ω ,0). In this study we compute the electronic γ (2 ω , ω , ω ,0) and β (2 ω , ω , ω ) for water molecules in liquid water using QM/MM calculations. The average value of γ (2 ω , ω , ω ,0) is smaller than the one for the gaz phase, and its standard deviation among the molecules is relatively small. In addition, we demonstrate that the average bulk second hyperpolarizability 〈 γ (2 ω , ω , ω ,0)〉 can be used to describe the electrostatic effects of the distant neighborhood on the first hyperpolarizability β (2 ω , ω , ω ). In comparison with more complex schemes to take into account long-range effects, the approximation is simple, and does not require any modifications of the QM/MM implementation. The long-range correction can be added explicitly, using an average value of γ for water in the condensed phase. It can also be easily added implicitly in QM/MM calculations through an additional embedding electric field, without the explicit calculation of γ .
Type of Medium:
Online Resource
ISSN:
1463-9076
,
1463-9084
Language:
English
Publisher:
Royal Society of Chemistry (RSC)
Publication Date:
2022
detail.hit.zdb_id:
1476283-3
detail.hit.zdb_id:
1476244-4
detail.hit.zdb_id:
1460656-2
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