4,684 research outputs found
One-body reduced density-matrix functional theory in finite basis sets at elevated temperatures
In this review we provide a rigorous and self-contained presentation of
one-body reduced density-matrix (1RDM) functional theory. We do so for the case
of a finite basis set, where density-functional theory (DFT) implicitly becomes
a 1RDM functional theory. To avoid non-uniqueness issues we consider the case
of fermionic and bosonic systems at elevated temperature and variable particle
number, i.e, a grand-canonical ensemble. For the fermionic case the Fock space
is finite-dimensional due to the Pauli principle and we can provide a rigorous
1RDM functional theory relatively straightforwardly. For the bosonic case,
where arbitrarily many particles can occupy a single state, the Fock space is
infinite-dimensional and mathematical subtleties (not every hermitian
Hamiltonian is self-adjoint, expectation values can become infinite, and not
every self-adjoint Hamiltonian has a Gibbs state) make it necessary to impose
restrictions on the allowed Hamiltonians and external non-local potentials. For
simple conditions on the interaction of the bosons a rigorous 1RDM functional
theory can be established, where we exploit the fact that due to the finite
one-particle space all 1RDMs are finite-dimensional. We also discuss the
problems arising from 1RDM functional theory as well as DFT formulated for an
infinite-dimensional one-particle space.Comment: 55 pages, 7 figure
Politiciansā Motivation, Political Culture, and Electoral Competition
We study electoral competition among politicians who are heterogeneous both in competence and in how much they care about (what they perceive as) the public interest relative to the private rents from being in office. We show that politiciansā incentives to behave opportunistically increase with politiciansā pay and with polarization of policy preferences. Moreover, politicians may have stronger incentives to behave opportunistically if other politicians are more likely to behave opportunistically. A political culture may therefore be selfreinforcing and multiple equilibria may arise. Lastly, we show that the mere probability that politicians care about the public interest enables opportunistic politicians to damage the reputation of their competitors. Consequently, efficient policies may be reversed.politiciansā motivation, politiciansā pay, political culture, electoral competition, coalition governments, reputation bashing
Structural relaxation in the hydrogen-bonding liquids N-methylacetamide and water studied by optical Kerr-effect spectroscopy
Structural relaxation in the peptide model N-methylacetamide (NMA) is studied
experimentally by ultrafast optical Kerr-effect spectroscopy over the
normal-liquid temperature range and compared to the relaxation measured in
water at room temperature. It is seen that in both hydrogen-bonding liquids,
beta relaxation is present and in each case it is found that this can be
described by the Cole-Cole function. For NMA in this temperature range, the
alpha and beta relaxations are each found to have an Arrhenius temperature
dependence with indistinguishable activation energies. It is known that the
variations on the Debye function, including the Cole-Cole function, are
unphysical, and we introduce two general modifications: one allows for the
initial rise of the function, determined by the librational frequencies, and
the second allows the function to be terminated in the alpha relaxation
Textural evolution and phase transformation in titania membranes: Part 1. -unsupported membranes
Textural evolution in solāgel derived nanostructured unsupported titania membranes has been studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), thermal gravimetry (TG), X-ray diffraction (XRD) and N2 adsorption. The anatase-to-rutile phase transformation kinetics were studied using the Avrami model. The precursor gel had a surface area of ca. 165 m2 gā1, which after heat treatment at 600 Ā°C for 8 h reduced to zero. Undoped titania-gel layers transformed to more than 95% rutile after calcination at 600 Ā°C for 8 h. The causes of surface-area reduction and pore growth were anatase crystallite growth and the enhanced sintering of rutile during transformation. Lanthanum oxide was identified as a suitable dopant for shifting the transformation temperature to ca. 850 Ā°C. Lanthanum oxide doped titania showed an improved stability of porous texture compared to that of the undoped titania membranes
Spectrum of slow and super-slow (picosecond to nanosecond) water dynamics around organic and biological solutes
Water dynamics in the solvation shell of solutes plays a very important role in the interaction of biomolecules and in chemical reaction dynamics. However, a selective spectroscopic study of the solvation shell is difficult because of the interference of the solute dynamics. Here we report on the observation of heavily slowed down water dynamics in the solvation shell of different solutes by measuring the low-frequency spectrum of solvation water, free from the contribution of the solute. A slowdown factor of ~50 is observed even for relatively low concentrations of the solute. We go on to show that the effect can be generalized to different solutes including proteins
Response calculations based on an independent particle system with the exact one-particle density matrix: polarizabilities
Recently, we have demonstrated that the problems finding a suitable adiabatic
approximation in time-dependent one-body reduced density matrix functional
theory can be remedied by introducing an additional degree of freedom to
describe the system: the phase of the natural orbitals [Phys. Rev. Lett. 105,
013002 (2010), J. Chem. Phys. 133, 174119 (2010)]. In this article we will show
in detail how the frequency-dependent response equations give the proper static
limit (), including the perturbation in the chemical potential,
which is required in static response theory to ensure the correct number of
particles. Additionally we show results for the polarizability for H and
compare the performance of two different two-electron functionals: the
phase-including L\"owdin-Shull functional and the density matrix form of the
L\"owdin-Shull functional.Comment: 10 pages, 6 figure
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