Paul A. Johnson
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View article: Richardson–Gaudin states of non-zero seniority. II. Single-reference treatment of strong correlation
Richardson–Gaudin states of non-zero seniority. II. Single-reference treatment of strong correlation Open
Strongly correlated systems are well described as a configuration interaction of Slater determinants classified by their number of unpaired electrons. This treatment is, however, unfeasible. In this paper, it is demonstrated that single re…
View article: Nitro and nitritosilanes: Do they and can they exist?
Nitro and nitritosilanes: Do they and can they exist? Open
NITROSILANES ARE UNKNOWN, MUCH LIKE THE NITRO ANALOGUES OF MOST METALLOIDS. THEIR NITRITE ISOMERS ARE BETTER KNOWN AND EVEN USED AS REAGENTS. STILL, MOST STUDIES ON NITRITOSILANES FOCUS ON REACTIVITIES AND THERE REMAINS SOME DOUBT ON THEIR…
View article: Synthesis of fluorinated phenylene-alkoxybenzothiadiazole polymer (PDTBTBz-2F <sub>anti</sub> ) by DHAP
Synthesis of fluorinated phenylene-alkoxybenzothiadiazole polymer (PDTBTBz-2F <sub>anti</sub> ) by DHAP Open
A new synthesis of PDTBTBz-2F anti was developed via DHAP using a partially biobased monomer. Two pathways were compared by DFT, experiments and OSC tests, benchmarked to Stille coupling, and preliminarily adapted to continuous-flow.
View article: Nitro and nitritosilanes: do they and can they exist?
Nitro and nitritosilanes: do they and can they exist? Open
We predict that nitrosilanes are unlikely to be stable under ambient conditions, while we prove spectroscopically and structurally that their thermodynamically favoured nitritosilanes isomers do exist.
View article: Singlet geminal wavefunctions
Singlet geminal wavefunctions Open
View article: Singlet Geminal Wavefunctions
Singlet Geminal Wavefunctions Open
Wavefunction forms based on products of electron pairs are usually constructed as closed-shell singlets, which is insufficient when the molecular state has a nonzero spin or when the chemistry is determined by $d$- or $f-$electrons. A set …
View article: Synthesis and conformational analysis of pyran inter-halide analogues of ᴅ-talose
Synthesis and conformational analysis of pyran inter-halide analogues of ᴅ-talose Open
In this work, we describe the synthesis of halogenated pyran analogues of ᴅ-talose using a halo-divergent strategy from known 1,6-anhydro-2,3-dideoxy-2,3-difluoro-β-ᴅ-mannopyranose. In solution and in the solid-state, all analogues adopt s…
View article: Synthesis and Conformational Analysis of Pyran Inter-Halide Analogues of D-Talose
Synthesis and Conformational Analysis of Pyran Inter-Halide Analogues of D-Talose Open
In this work, we describe the synthesis of halogenated pyran analogues of D-talose using a halo-divergent strategy from known 1,6-anhydro-2,3-dideoxy-2,3-difluoro-β-D-mannopyranose. In solution and in the solid-state, all analogues adopt s…
View article: Beyond a Richardson-Gaudin mean-field: Slater-Condon rules and perturbation theory
Beyond a Richardson-Gaudin mean-field: Slater-Condon rules and perturbation theory Open
Richardson-Gaudin states provide a basis of the Hilbert space for strongly correlated electrons. In this study, optimal expressions for the transition density matrix elements between Richardson-Gaudin states are obtained with a cost compar…
View article: Parameters Influencing the Photochemical Cyclodehydrochlorination (CDHC) Reaction
Parameters Influencing the Photochemical Cyclodehydrochlorination (CDHC) Reaction Open
The photochemical cyclodehydrochlorination (CDHC) reaction has recently been used to prepare a wide variety of polycyclic aromatic hydrocarbons and graphene nanoribbons (GNRs). However, the parameters affecting the efficiency of this react…
View article: Richardson-Gaudin States
Richardson-Gaudin States Open
This chapter gives an overview of Richardson-Gaudin states which represent weakly correlated pairs of electrons. They are parametrized by sets of numbers obtained from non-linear equations. The best method to solve these equations is prese…
View article: Single reference treatment of strongly correlated H$_4$ and H$_{10}$ isomers with Richardson-Gaudin states
Single reference treatment of strongly correlated H$_4$ and H$_{10}$ isomers with Richardson-Gaudin states Open
Richardson-Gaudin (RG) states are employed as a variational wavefunction ansatz for strongly correlated isomers of H$_4$ and H$_{10}$. In each case a single RG state describes the seniority-zero sector quite well. Simple natural orbital fu…
View article: Integrated system for investigating sub-surface features of a rock formation
Integrated system for investigating sub-surface features of a rock formation Open
A system for investigating non-linear properties of a rock formation around a borehole is provided. The system includes a first sub-system configured to perform data acquisition, control and recording of data; a second subsystem in communi…
View article: System and method for generating micro-seismic events and characterizing properties of a medium with non-linear acoustic interactions
System and method for generating micro-seismic events and characterizing properties of a medium with non-linear acoustic interactions Open
A method and system includes generating a first coded acoustic signal including pulses each having a modulated signal at a central frequency; and a second coded acoustic signal each pulse of which includes a modulated signal a central freq…
View article: System and method for investigating sub-surface features of a rock formation with acoustic sources generating conical broadcast signals
System and method for investigating sub-surface features of a rock formation with acoustic sources generating conical broadcast signals Open
A method of interrogating a formation includes generating a conical acoustic signal, at a first frequency--a second conical acoustic signal at a second frequency each in the between approximately 500 Hz and 500 kHz such that the signals in…
View article: System and method for investigating sub-surface features and 3D imaging of non-linear property, compressional velocity VP, shear velocity VS and velocity ratio VP/VS of a rock formation
System and method for investigating sub-surface features and 3D imaging of non-linear property, compressional velocity VP, shear velocity VS and velocity ratio VP/VS of a rock formation Open
A system and a method for generating a three-dimensional image of a rock formation, compressional velocity VP, shear velocity VS and velocity ratio VP/VS of a rock formation are provided. A first acoustic signal includes a first plurality …
View article: System and method for generating 3D images of non-linear properties of rock formation using surface seismic or surface to borehole seismic or both
System and method for generating 3D images of non-linear properties of rock formation using surface seismic or surface to borehole seismic or both Open
A system and method of characterizing properties of a medium from a non-linear interaction are include generating, by first and second acoustic sources disposed on a surface of the medium on a first line, first and second acoustic waves. T…
View article: CCDC 2171948: Experimental Crystal Structure Determination
CCDC 2171948: Experimental Crystal Structure Determination Open
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available …
View article: Density matrices of seniority-zero geminal wavefunctions
Density matrices of seniority-zero geminal wavefunctions Open
Scalar products and density matrix elements of closed-shell pair geminal wavefunctions are evaluated directly in terms of the pair amplitudes, resulting in an analog of Wick’s theorem for fermions or bosons. This expression is, in general,…
View article: Near-exact treatment of seniority-zero ground and excited states with a Richardson–Gaudin mean-field
Near-exact treatment of seniority-zero ground and excited states with a Richardson–Gaudin mean-field Open
Eigenvectors of the reduced Bardeen–Cooper–Schrieffer (BCS) Hamiltonian, Richardson–Gaudin (RG) states, are used as a variational wavefunction ansatz for strongly correlated electronic systems. These states are geminal products whose coeff…
View article: Bivariational Principle for an Antisymmetrized Product of Nonorthogonal Geminals Appropriate for Strong Electron Correlation
Bivariational Principle for an Antisymmetrized Product of Nonorthogonal Geminals Appropriate for Strong Electron Correlation Open
We develop a bivariational principle for an antisymmetric product of nonorthogonal geminals. Special cases reduce to the antisymmetric product of strongly-orthogonal geminals (APSG), the generalized valence bond-perfect pairing (GVB-PP), a…
View article: Near-exact treatment of seniority-zero ground and excited states with a\n Richardson-Gaudin mean-field
Near-exact treatment of seniority-zero ground and excited states with a\n Richardson-Gaudin mean-field Open
Eigenvectors of the reduced Bardeen-Cooper-Schrieffer Hamiltonian,\nRichardson-Gaudin (RG) states, are used as a variational wavefunction Ansatz\nfor strongly-correlated electronic systems. These states are geminal products\nwhose coeffici…
View article: Perturbative corrections for Hartree-Fock-like Algebraic Bethe Ansatz analogue
Perturbative corrections for Hartree-Fock-like Algebraic Bethe Ansatz analogue Open
Rayleigh Schrödinger perturbation theory corrections are developed for an algebraic Bethe ansatz of individual electrons. Numerical results are ambiguous and would need either an orbital optimization or a configuration interaction singles …
View article: Transition density matrices of Richardson–Gaudin states
Transition density matrices of Richardson–Gaudin states Open
Recently, ground state eigenvectors of the reduced Bardeen–Cooper–Schrieffer (BCS) Hamiltonian, Richardson–Gaudin (RG) states, have been employed as a wavefunction ansatz for strong correlation. This wavefunction physically represents a me…
View article: Fluorine effect in nucleophilic fluorination at C4 of 1,6-anhydro-2,3-dideoxy-2,3-difluoro-β-D-hexopyranose
Fluorine effect in nucleophilic fluorination at C4 of 1,6-anhydro-2,3-dideoxy-2,3-difluoro-β-D-hexopyranose Open
In this work, we have developed a simple synthetic approach using Et 3 N·3HF as an alternative to the DAST reagent. We controlled the stereochemistry of the nucleophilic fluorination at C4 of 1,6-anhydro-2,3-dideoxy-2,3-difluoro-4- O -trif…
View article: Richardson-Gaudin geminal wavefunctions in a Slater determinant basis
Richardson-Gaudin geminal wavefunctions in a Slater determinant basis Open
View article: Reduced density matrices of Richardson–Gaudin states in the Gaudin algebra basis
Reduced density matrices of Richardson–Gaudin states in the Gaudin algebra basis Open
Eigenvectors of the reduced Bardeen–Cooper–Schrieffer Hamiltonian have recently been employed as a variational wavefunction ansatz in quantum chemistry. This wavefunction is a mean-field of pairs of electrons (geminals). In this contributi…
View article: Richardson–Gaudin mean-field for strong correlation in quantum chemistry
Richardson–Gaudin mean-field for strong correlation in quantum chemistry Open
Ground state eigenvectors of the reduced Bardeen–Cooper–Schrieffer Hamiltonian are employed as a wavefunction Ansatz to model strong electron correlation in quantum chemistry. This wavefunction is a product of weakly interacting pairs of e…
View article: Reduced density matrices of Richardson-Gaudin states in the Gaudin\n algebra basis
Reduced density matrices of Richardson-Gaudin states in the Gaudin\n algebra basis Open
Eigenvectors of the reduced Bardeen-Cooper-Schrieffer Hamiltonian have\nrecently been employed as a variational wavefunction ansatz in quantum\nchemistry. This wavefunction is a mean-field of pairs of electrons (geminals).\nIn this contrib…
View article: Synthesis and Properties of Conjugated Polymers Based on a Ladderized Anthanthrene Unit
Synthesis and Properties of Conjugated Polymers Based on a Ladderized Anthanthrene Unit Open
Polycyclic aromatic hydrocarbons (PAHs) are interesting building blocks for the preparation of conjugated polymers due to their extended π surface and planar conformation. However, their use as comonomer in conjugated polymers often leads …