Trimethylphosphine

Luetkens, Melvin L.; Sattelberger, Alfred P.; Murray, H. H.; Basil, J. D.; Fackler, John P.; Jones, Richard A.; Heaton, Duane E.

doi:10.1002/9780470132593.ch76

Cited by 37 publications

(26 citation statements)

References 13 publications

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“…Estimated ordered moments for LaFePO, BaFs 2 As 2 and FeTe are also all consistent with the experiments [10,11,[30][31][32][33]. The relevance of quantum criticality is a recent subject of debates [34][35][36]. The present work supports its relevance.…”

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confidence: 88%

Magnetic Properties of Ab initio Model of Iron-Based Superconductors LaFeAsO

2011

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By using a variational Monte Carlo method, we examine an effective low-energy model for LaFeAsO derived from an ab initio downfolding scheme. We show that quantum and many-body fluctuations near the antiferromagnetic (AF) quantum critical point largely reduce the antiferromagnetic ordered moment. Our derived model not only quantitatively reproduces the small ordered moment in LaFeAsO, but also accounts for the diversity from LaFePO, BaFe 2 As 2 to FeTe. Electron correlation is found to determine the observed material dependence. We also find that LaFeAsO is subject to large orbital fluctuations, sandwiched by the AF Mott insulator and weakly correlated metals. The orbital fluctuations and Dirac-cone dispersion hold keys for the diverse magnetic properties.KEYWORDS: iron-based superconductors, first-principle calculation, variational Monte Carlo method, quantum critical point, Dirac-cone dispersionThe discovery of iron-based superconductors has renewed interest in the mechanisms of high-T c superconductivity. 1)Roles of electron correlations in the iron-based families and in the pairing mechanisms are focus of intensive debate. 2-9)An aspect common in these families is the nearby antiferromagnetic (AF) phases, similar to those in cuprate high-T c superconductors. In the iron-based families, however, the AF orders are found in metals and show a variety of ordered moments ranging from $2 B with a bicollinear order for FeTe [10][11][12] to 0.3-0.6 B with an AF stripe (AFS) order for LaFeAsO. 13,14) Since ab initio density-functional calculations usually underestimate AF moments, it is unconventional that the measured moment for LaFeAsO is substantially smaller than the density-functional estimate of 1.2-2.6 B .15-18) It strongly suggests the necessity of considering quantum fluctuations beyond the mean-field level.A difficulty in the iron-based superconductors comes from their entangled band structure composed of five Fe-3d bands near the Fermi level.18) The recently proposed three-stage scheme, consisting of the derivation of global band structure by the conventional density functional calculations, ab initio downfolding scheme to derive low-energy models, and the scheme for solving the resultant realistic models by appropriate low-energy solvers, has opened a way of analyzing such a real complexity of materials. 19,20) This scheme has already been applied to the iron-based families, and effective low-energy models have been derived. 21,22) The next step of solving the effective models using reliable low-energy solvers is so far mostly confined to that by the dynamical mean-field approximation (DMFA), 3,7,8) where spatial correlation effects are hardly analyzed in the present multiorbital systems.To understand the correlation effects and the unconventional magnetism described above, interplays of orbitals and spins have to be elucidated by considering spatial fluctuations beyond DMFA. For this purpose, many-variable variational Monte Carlo (VMC) method, 23) combined with quantum-number projection, 24) offers a suit...

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confidence: 88%

Magnetic Properties of Ab initio Model of Iron-Based Superconductors LaFeAsO

2011

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“…Trimethylmethylene phosphorane (Ylide), trimethyl(trimethylsilylmethylene) phosphorane (TMS‐ylide), (THT)AuCl, (PMe 3 )AuCl, and N , N′ ‐di‐ tert ‐butylimidazolidinium chloride were prepared according to literature procedures. Trimethylphosphine (PMe 3 ) was prepared by the literature procedure using iodomethane instead of bromomethane . Tetrahydrothiophene pentafluorophenylgold(I), (THT)AuC 6 F 5 , was prepared using chloropentafluorophenylbenzene instead of the bromo‐ derivative .…”

Section: Methodsmentioning

confidence: 99%

Controlling the Thermal Stability and Volatility of Organogold(I) Compounds for Vapor Deposition with Complementary Ligand Design

et al. 2019

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Atomic layer deposition (ALD) of gold is being studied by multiple research groups, but to date no process using non‐energetic co‐reactants has been demonstrated. In order to access milder co‐reactants, precursors with higher thermal stability are required. We set out to uncover how structure and bonding affect the stability and volatility of a family of twelve organogold(I) compounds using a combination of techniques: X‐ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and density functional theory (DFT). Small, unsubstituted phosphonium ylide ligands bind more strongly to Au(I) than their silyl‐substituted analogues, but the utility of both these ligands suffers due to their poor volatility and substantial thermal decomposition. Pentafluorophenyl (C6F5) is introduced as a new, very electronegative ligand for gold vapor deposition precursors, and it was found that the disadvantage to volatility due to π‐stacking and other intermolecular interactions in the solid state was overshadowed by dramatic improvements to kinetic and thermodynamic stability. We introduce a new figure of merit to compare and rank the suitability of these and other complexes as precursors for vapor deposition. Finally, DFT calculations on four compounds that have high figures of merit show a linear correlation between the gold‐coordinative ligand bond dissociation energies and the observed decomposition temperatures, highlighting and justifying this design strategy.

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“…Solvents were distilled under nitrogen from sodium benzophenone (pentane and diethyl ether) or from sodium (toluene) immediately before use. The compounds Th(BH 4 ) 4 (Et 2 O) 2 [12], trimethylphosphine [29], triethylphosphine [30], and 1,2-bis(dimethylphosphino)ethane [31] were prepared by literature routes.…”

Section: Methodsmentioning

confidence: 99%