Ampliación de Química Cuántica. Capítulo 1: Repaso a los conceptos vistos de Química Cuántica

Ampliación de Química Cuántica: Tema 1.

La ciencia y la palabra mágica. Confluencias del realismo mágico y la física cuántica en Kenzaburō Ōe y Haruki Murakami

Las relaciones literarias entre la cultura latinoamericana y la japonesa no han disfrutado del desarrollo que han tenido los estudios comparatistas centrados en los intercambios de Occidente con Japón. Este estudio pretende incidir en la influencia del realismo mágico literario latinoamericano en Japón a través de momentos puntuales en la escritura de K. Oé (M/T y la historia de las maravillas del bosque) y H. Murakami (Kafka en la orilla, 1Q84). A pesar de que este último autor sí ha sido analizado desde los postulados del realismo mágico, aquí discutimos sus resultados interpretativos. Más bien lo adscribimos al ámbito de la literatura fantástica, sin renunciar al análisis de sus mundos con modelos ficcionales inspirados en la física cuántica, por lo que aplicamos a sus novelas el principio de incertidumbre y las consecuencias de la no-localidad y de la dualidad 'onda-partícula'. En cuanto a K. Oé, nos aproximamos a su novela desde los presupuestos de la llamada «ética cuántica» para justificar cómo el realismo mágico coincide en ciertas intuiciones con lo descrito por la física cuántica. Desde esa perspectiva, lo inverosímil (bajo el paradigma newtoniano) se torna (en el paradigma cuántico) verosímil, y en el proceso se amplía el concepto de realismo.

Spin alignment of extra electrons in K-phenanthrene clusters taken from the crystalline tripotassium-intercalated phenanthrene structure

The appearance of ferromagnetic correlations among π electrons of phenanthrene (C14H10) molecules in the herringbone structure is proven for K doped clusters both by ab initio quantum-chemistry calculations and by the direct solution of the many-body Pariser-Parr-Pople Hamiltonian. Magnetic ground states are predicted for one or three additional electrons per phenanthrene molecule. These results are a consequence of the small overlap between the lowest unoccupied molecular orbitals (and lowest unoccupied molecular orbitals + 1) of neutral neighboring phenanthrene molecules, which makes the gain in energy by delocalization similar to the corresponding increase due to the Coulomb interaction.

Exponential decay of spin-spin correlation between distant defect states produced by contour hydrogenation of polycyclic aromatic hydrocarbon molecules

The first few low-lying spin states of alternant polycyclic aromatic hydrocarbon (PAH) molecules of several shapes showing defect states induced by contour hydrogenation have been studied both by ab initio methods and by a precise numerical solution of Pariser-Parr-Pople (PPP) interacting model. In accordance with Lieb's theorem, the ground state shows a spin multiplicity equal to one for balanced molecules, and it gets larger values for imbalanced molecules (that is, when the number of π electrons on both subsets is not equal). Furthermore, we find a systematic decrease of the singlet-triplet splitting as a function of the distance between defects, regardless of whether the ground state is singlet or triplet. For example, a splitting smaller than 0.001 eV is obtained for a medium size C46H28 PAH molecule (di-hydrogenated [11]phenacene) showing a singlet ground state. We conclude that π electrons unbound by lattice defects tend to remain localized and unpaired even when long-range Coulomb interaction is taken into account. Therefore they show a biradical character (polyradical character for more than two defects) and should be studied as two or more local doublets. The implications for electron transport are potentially important since these unpaired electrons can trap traveling electrons or simply flip their spin at a very small energy cost.