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Within this framework, using ab initio PIMD simulations, we compute phonon dispersions of diamond and of the high-pressure I41/amd phase of atomic hydrogen. We find that in the latter case, the anharmonicity is stronger than previously estimated and yields a sizeable red-shift in the vibrational spectrum of atomic hydrogen.We develop a model of interacting zwitterionic membranes with rotating surface dipoles immersed in a monovalent salt and implement it in a field theoretic formalism. In the mean-field regime of monovalent salt, the electrostatic forces between the membranes are characterized by a non-uniform trend at large membrane separations, the interfacial dipoles on the opposing sides behave as like-charge cations and give rise to repulsive membrane interactions; at short membrane separations, the anionic field induced by the dipolar phosphate groups sets the behavior in the intermembrane region. The attraction of the cationic nitrogens in the dipolar lipid headgroups leads to the adhesion of the membrane surfaces via dipolar bridging. The underlying competition between the opposing field components of the individual dipolar charges leads to the non-uniform salt ion affinity of the zwitterionic membrane with respect to the separation distance; large inter-membrane separations imply anionic excess, while small nanometer-sized separations favor cationic excess. This complex ionic selectivity of zwitterionic membranes may have relevant repercussions on nanofiltration and nanofluidic transport techniques.The recently discovered positronic molecule e+H- 2 [J. Charry et al., Angew. Chem., Int. Ed. Navitoclax in vivo 57, 8859-8864 (2018)] has a new type of bond, the single-positron bond. We studied its stability using quantum Monte Carlo techniques. We computed an accurate potential energy curve of the reaction H- + PsH → e+H- 2 → H2 + Ps- to establish its global stability with respect to all possible dissociation channels and to define the range of its local stability. We showed that the e+H- 2 system is stable with respect to the dissociation into H- + PsH, with a binding energy of 23.5(1) mhartree. For R less then 3.2 bohrs, the system is unstable, and it decays into H2 + Ps-. There are no other bound structures for R less then 3.2 bohrs. We discuss possible routes to its experimental production.Ensembles of ab initio parameterized Frenkel-exciton model Hamiltonians for different perylene diimide dimer systems are used, together with various dissipative quantum dynamics approaches, to study the influence of the solvation environment and fluctuations in chromophore relative orientation and packing on the vibronic spectra of two different dimer systems a π-stacked dimer in aqueous solution in which the relative chromophore geometry is strongly confined by a phosphate bridge and a side-by-side dimer in dichloromethane involving a more flexible alkyne bridge that allows quasi-free rotation of the chromophores relative to one another. These entirely first-principles calculations are found to accurately reproduce the main features of the experimental absorption spectra, providing a detailed mechanistic understanding of how the structural fluctuations and environmental interactions influence the vibronic dynamics and spectroscopy of solutions of these multi-chromophore complexes.This Editorial reports how the depletion force theory was originally developed by Sho Asakura and Fumio Oosawa and how their one-page paper was "rediscovered" about 20 years after the paper was published. The first part of this Editorial is mostly based on the lecture by Oosawa and his autobiographies, and the second part is written by one of two scientists who found the paper. The aim of this Editorial is to record the background of the discovery of the depletion force. We believe that this Editorial presents an interesting story showing how science develops. The story reminds us of the importance of basic education and continuous interests in unknown phenomena and interactions between people of different disciplines, although they are sometimes considered as separate elements of research.There has been recent interest in the deployment of ab initio density matrix renormalization group (DMRG) computations on high performance computing platforms. Here, we introduce a reformulation of the conventional distributed memory ab initio DMRG algorithm that connects it to the conceptually simpler and advantageous sum of the sub-Hamiltonian approach. Starting from this framework, we further explore a hierarchy of parallelism strategies that includes (i) parallelism over the sum of sub-Hamiltonians, (ii) parallelism over sites, (iii) parallelism over normal and complementary operators, (iv) parallelism over symmetry sectors, and (v) parallelism within dense matrix multiplications. We describe how to reduce processor load imbalance and the communication cost of the algorithm to achieve higher efficiencies. We illustrate the performance of our new open-source implementation on a recent benchmark ground-state calculation of benzene in an orbital space of 108 orbitals and 30 electrons, with a bond dimension of up to 6000, and a model of the FeMo cofactor with 76 orbitals and 113 electrons. The observed parallel scaling from 448 to 2800 central processing unit cores is nearly ideal.The present work intends to join and respond to the excellent and thoroughly documented rovibrational study of X. G. Wang and T. Carrington, Jr. [J. Chem. Phys. 154, 124112 (2021)] that used an approach tailored for floppy dimers with an analytic dimer Hamiltonian and a non-product basis set including Wigner D functions. It is shown in the present work that the GENIUSH black-box-type rovibrational method can approach the performance of the tailor-made computation for the example of the floppy methane-water dimer. Rovibrational transition energies and intensities are obtained in the black-box-type computation with a twice as large basis set and in excellent numerical agreement in comparison with the more efficient tailor-made approach.The microscopic doping mechanism behind the superconductor-to-insulator transition of a thin film of YBa2Cu3O7 was recently identified as due to the migration of O atoms from the CuO chains of the film. Here, we employ density-functional theory calculations to study the evolution of the electronic structure of a slab of YBa2Cu3O7 in the presence of oxygen vacancies under the influence of an external electric field. We find that, under massive electric fields, isolated O atoms are pulled out of the surface consisting of CuO chains. As vacancies accumulate at the surface, a configuration with vacancies located in the chains inside the slab becomes energetically preferred, thus providing a driving force for O migration toward the surface. Regardless of the defect configuration studied, the electric field is always fully screened near the surface, thus negligibly affecting diffusion barriers across the film.
Here's my website: https://www.selleckchem.com/products/ABT-263.html
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