Ketamine

No AbstractKeywords: Ketamin

Too-many-solutions and Reference to Position in Serial OT

Any OT constraint banning a phonological entity in some position predicts that two types of languages should be attested: the ones which satisfy the constraint by changing the marked element and the ones where position of a marked element is modified. Yet for most such constraints, the languages which modify the marked element are attested but the ones modifying the position are not. The paper proposes a way to principally solve this problem within the framework of Serial OT. The solution consists in replacing the relevant OT constraints with constraints that specify position in the output of the previous derivational step (PS-constraints). Modifying position does not improve on PS-constraints since position in the output is irrelevant to their violation profile and position in the previous step cannot be changed by Gen. Adopting PS-constraints makes phonological theory more restrictive in a way that is compatible with the attested typology in the domain of voicing neutralization and syncope-stress interaction. The theory of PS-constraints is grounded in a precise definition of phonological position. If a constraint C mentions the elements of prosodic hierarchy both below and above the segmental level, the elements above the segmental level constitute position

Noninteracting v-Representable Subspaces of Orbitals in the Kohn–Sham Method

The notion of noninteracting v-representability is extended from electron densities to finite-dimensional linear subspaces of orbitals. Unlike electron densities, orbital subspaces can be tested for noninteracting v-representability using a transparent necessary condition: the subspace must be invariant under the action of some one-electron Kohn–Sham Hamiltonian. This condition allows one to determine in principle, and sometimes in practice, whether a given one-electron basis set can represent an N-electron density within the Kohn–Sham method and to find the corresponding Kohn–Sham effective potential v if it exists. If the occupied Kohn–Sham orbitals form linearly independent products, then their subspace is determined by the corresponding ground-state electron density. This means that the Kohn–Sham effective potential corresponding to certain finite-basis-set electron densities can be deduced from the basis set itself

Uniform electron gas limit of an exact expression for the Kohn–Sham exchange-correlation potential

Previously, we derived an exact formula for the Kohn–Sham exchange-correlation potential corresponding, in the basis-set limit, to the Hartree–Fock electron density of a given system. This formula expresses the potential in terms of the occupied Hartree–Fock and Kohn–Sham orbitals and orbital energies. Here, we show that, when applied to the Hartree–Fock description of a uniform electron gas, the formula correctly reduces to the exchange-only local density approximation

Reconstruction of Exchange–Correlation Potentials from Their Matrix Representations

Within a basis set of one-electron functions that form linearly independent products (LIPs), it is always possible to construct a unique local (multiplicative) real-space potential that is precisely equivalent to an arbitrary given operator. Although standard basis sets of quantum chemistry rarely form LIPs in a numerical sense, occupied and low-lying virtual canonical Kohn–Sham orbitals often do so, at least for small atoms and molecules. Using these principles, we construct atomic and molecular exchange–correlation potentials from their matrix representations in LIP basis sets of occupied canonical Kohn–Sham orbitals. The reconstructions are found to imitate the original potentials in a consistent but exaggerated way. Since the original and reconstructed potentials produce the same ground-state electron density and energy within the associated LIP basis set, the procedure may be regarded as a rigorous solution to the Kohn–Sham inversion problem within the subspace spanned by the occupied Kohn–Sham orbitals

Searching for stable fullerenes in space with computational chemistry

We report a computational study of the stability and infrared (IR) vibrational spectra of neutral and singly ionised fullerene cages containing between 44 and 70 carbon atoms. The stability is characterised in terms of the standard enthalpy of formation per CC bond, the HOMO-LUMO gap, and the energy required to eliminate a C$_2$ fragment. We compare the simulated IR spectra of these fullerene species to the observed emission spectra of several planetary nebulae (Tc 1, SMP SMC 16, and SMP LMC 56) where strong C$_{60}$ emission has been detected. Although we could not conclusively identify fullerenes other than C$_{60}$ and C$_{70}$, our results point to the possible presence of smaller (44, 50, and 56-atom) cages in those astronomical objects. Observational confirmation of our prediction should become possible when the James Webb Space Telescope comes online.Comment: 11 pages, 13 figures, 1 table. Accepted for publication on MNRA

Exact expressions for the Kohn–Sham exchange-correlation potential in terms of wave-function-based quantities

Several workers have deduced various exact expressions for the Kohn–Sham exchange-correlation potential in terms of quantities computable from the interacting and noninteracting wave functions of the system. We show that all these expressions can be obtained by one general method in which the interacting N-electron wave function is expanded in products of one- and (N − 1)-electron functions. Different expressions correspond to different choices of the latter functions. Our analysis unifies and clarifies the previously proposed exact treatments of the exchange-correlation potential, and suggests new ways of expressing this quantity