skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: DMRG-CASPT2 study of the longitudinal static second hyperpolarizability of all-trans polyenes

Abstract

We have implemented internally contracted complete active space second order perturbation theory (CASPT2) with the density matrix renormalization group (DMRG) as active space solver [Y. Kurashige and T. Yanai, J. Chem. Phys. 135, 094104 (2011)]. Internally contracted CASPT2 requires to contract the generalized Fock matrix with the 4-particle reduced density matrix (4-RDM) of the reference wavefunction. The required 4-RDM elements can be obtained from 3-particle reduced density matrices (3-RDM) of different wavefunctions, formed by symmetry-conserving single-particle excitations op top of the reference wavefunction. In our spin-adapted DMRG code CHEMPS2https://github.com/sebwouters/chemps2, we decompose these excited wavefunctions as spin-adapted matrix product states and calculate their 3-RDM in order to obtain the required contraction of the generalized Fock matrix with the 4-RDM of the reference wavefunction. In this work, we study the longitudinal static second hyperpolarizability of all-trans polyenes C{sub 2n}H{sub 2n+2} [n = 4–12] in the cc-pVDZ basis set. DMRG-SCF and DMRG-CASPT2 yield substantially lower values and scaling with system size compared to RHF and MP2, respectively.

Authors:
; ;  [1]
  1. Center for Molecular Modelling, Ghent University, Technologiepark 903, 9052 Zwijnaarde (Belgium)
Publication Date:
OSTI Identifier:
22678969
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 145; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DENSITY MATRIX; PERTURBATION THEORY; POLYENES; WAVE FUNCTIONS

Citation Formats

Wouters, Sebastian, Van Speybroeck, Veronique, and Van Neck, Dimitri. DMRG-CASPT2 study of the longitudinal static second hyperpolarizability of all-trans polyenes. United States: N. p., 2016. Web. doi:10.1063/1.4959817.
Wouters, Sebastian, Van Speybroeck, Veronique, & Van Neck, Dimitri. DMRG-CASPT2 study of the longitudinal static second hyperpolarizability of all-trans polyenes. United States. doi:10.1063/1.4959817.
Wouters, Sebastian, Van Speybroeck, Veronique, and Van Neck, Dimitri. Sun . "DMRG-CASPT2 study of the longitudinal static second hyperpolarizability of all-trans polyenes". United States. doi:10.1063/1.4959817.
@article{osti_22678969,
title = {DMRG-CASPT2 study of the longitudinal static second hyperpolarizability of all-trans polyenes},
author = {Wouters, Sebastian and Van Speybroeck, Veronique and Van Neck, Dimitri},
abstractNote = {We have implemented internally contracted complete active space second order perturbation theory (CASPT2) with the density matrix renormalization group (DMRG) as active space solver [Y. Kurashige and T. Yanai, J. Chem. Phys. 135, 094104 (2011)]. Internally contracted CASPT2 requires to contract the generalized Fock matrix with the 4-particle reduced density matrix (4-RDM) of the reference wavefunction. The required 4-RDM elements can be obtained from 3-particle reduced density matrices (3-RDM) of different wavefunctions, formed by symmetry-conserving single-particle excitations op top of the reference wavefunction. In our spin-adapted DMRG code CHEMPS2https://github.com/sebwouters/chemps2, we decompose these excited wavefunctions as spin-adapted matrix product states and calculate their 3-RDM in order to obtain the required contraction of the generalized Fock matrix with the 4-RDM of the reference wavefunction. In this work, we study the longitudinal static second hyperpolarizability of all-trans polyenes C{sub 2n}H{sub 2n+2} [n = 4–12] in the cc-pVDZ basis set. DMRG-SCF and DMRG-CASPT2 yield substantially lower values and scaling with system size compared to RHF and MP2, respectively.},
doi = {10.1063/1.4959817},
journal = {Journal of Chemical Physics},
number = 5,
volume = 145,
place = {United States},
year = {Sun Aug 07 00:00:00 EDT 2016},
month = {Sun Aug 07 00:00:00 EDT 2016}
}
  • Improved equipment for measurements of the electrooptical Kerr effect in gases is described, and a study of carbon dioxide over a range of temperatures ({approx}299-490 K) and pressures ({approx}100-1000 kPa) is reported. Analysis of the temperature dependence of the effect yields definitive values for the second Kerr hyperpolarizability (10{sup 60}{gamma}{sup K}/C m{sup 4} V{sup {minus}3} = 0.125 {plus minus} 0.032) and the static polarizability anisotropy (10{sup 40}{Delta}{alpha}{degree}/C m{sup 2} V{sup {minus}1} = 2.41 {plus minus} 0.08) of the carbon dioxide molecule, and these are compared with discordant results from other sources.
  • We report reaction paths starting from N({sup 2}D) + H{sub 2}O for doublet spin states, D{sub 0} and D{sub 1}. The potential energy surfaces are explored in an automated fashion using the global reaction route mapping strategy. The critical points and reaction paths have been fully optimized at the complete active space second order perturbation theory level taking all valence electrons in the active space. In addition to direct dissociation pathways that would be dominant, three roaming processes, two roaming dissociation, and one roaming isomerization: (1) H{sub 2}ON → H–O(H)N → H–HON → NO({sup 2}Π) + H{sub 2}, (2) cis-HNOHmore » → HNO–H → H–HNO → NO + H{sub 2}, (3) H{sub 2}NO → H–HNO → HNO–H → trans-HNOH, are confirmed on the D{sub 0} surface.« less
  • Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonicalmore » nucleobases fragmentations of N–H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N–H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π{sub 1}{sup −} and π{sub 2}{sup −} states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.« less
  • Sequential ring-opening metathesis polymerization of norbornene and 7,8-bis(trifluoromethyl)tricyclo[4.2.2.0[sup 2.5]]-deca-3,7,9-triene with Mo(CHCMe[sub 3])(NAr)(OCMe[sub 3])[sub 2] (Ar = 2,6-diisopropylphenyl) followed by linking termination with a conjugated dialdehyde results in highly soluble A-B-A triblock copolymers containing an oligomer of a precursor of Durham polyacetylene as the central block. Subsequent heat treatment converts the polyacetylene precursors into model polyenes. A series of these copolymers that had conjugation lengths ranging from 4 to 16 double bonds was synthesized. The polyenes were isomerized to the predominantly all-trans isomer. The presence of the polynorbornene chains solubilizes the polyenes, allowing their hyperpolarizability to be probed with electric fieldmore » induced second harmonic generation; [gamma][sub N]([minus]2[omega][sup [sm bullet]],[omega][omega],0) and [gamma][sub N](0) varied with conjugation length to the 3.6 and 3.2 powers, respectively. 54 refs., 8 figs., 4 tabs.« less