Search query: AX center first principle

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abstract: The vibrational properties of the wurtzstannite \text{Cu}}_{2}\text{ZnGeS}}_{4} are studied experimentally by polarized Raman scattering in off resonant and resonant conditions and theoretically by ab initio lattice dynamics calculations. Twenty nine modes from 45 Raman active theoretically predicted have been experimentally detected and identified, including polar \text{A}}_{1}(TO) \text{A}}_{1}(LO) and \text{B}}_{1}(TO+LO)\text{B}}_{2}(TO+LO) and nonpolar \text{A}}_{2} symmetry phonon modes from measurements on (2 1 0) and (0 0 1) crystallographic planes of \text{Cu}}_{2}\text{ZnGeS}}_{4} single crystals. The lattice dynamics calculations provide a full picture of the zone center phonon spectrum and allow the assignment of experimentally observed lines to first and second order lattice vibrations. Using resonance Raman conditions, a strong enhancement of the \text{A}}_{1}(LO) modes with the highest longitudinal transversal spiting is observed.
author_names: Maxim Guc

Alexander P Litvinchuk

S Levcenko

Victor Izquierdo-Roca

Xavier Fontane

Mykhailo Ya Valakh

E K Arushanov

Alejandro Perez-Rodriguez
title: Optical phonons in the wurtzstannite Cu 2 ZnGeS 4 semiconductor: Polarized Raman spectroscopy and first principle calculations
year: 2014

abstract: By applying the Born Huang expansion, originally developed for coupled nucleus electron systems, to the full nucleus electron photon Hamiltonian of non relativistic quantum electrodynamics (QED) in the long wavelength approximation, we deduce an exact set of coupled equations for electrons on photonic energy surfaces and the nuclei on the resulting polaritonic energy surfaces. This theory describes seamlessly many body interactions between nuclei, electrons and photons including the quantum fluctuation of the electromagnetic field and provides a proper first principle framework to describe QED chemistry phenomena. Since the photonic surfaces and the corresponding non adiabatic coupling elements can be solved analytically, the resulting expansion can be brought into a compact form which allows us to analyze aspects of coupled nucleus electron photon systems in a simple and intuitive manner. Furthermore, we discuss structural differences between the exact quantum treatment and Floquet theory and show how existing implementations of Floquet theory can be adjusted to adhere to QED. From this generalized Born Huang expansion an adapted Born Oppenheimer approximation for nuclei on polaritonic surfaces can be deduced. This form allows a direct application of first principle methods of quantum chemistry such as coupled cluster or configuration interaction approaches to QED chemistry. By restricting the basis set of this generalized Born Oppenheimer approximation we furthermore bridge quantum chemistry and quantum optics by recovering simple models of coupled matter photon systems employed in quantum optics and polaritonic chemistry. We finally highlight numerically that simple few level models can lead to physically wrong predictions, even in weak coupling regimes, and show how the presented derivations from first principles help to check and derive physically reliable simplified models.
author_names: Christian Schafer

Michael Ruggenthaler

Angel Rubio Max Planck Institute for the Structure

Dynamics of Matter

Center for High Energy Physics
title: Ab initio nonrelativistic quantum electrodynamics: Bridging quantum chemistry and quantum optics from weak to strong coupling
year: 2018

abstract: A new module, which includes both the turbulence electron heating and the electron neutral cooling rate correction associated with the Farley Buneman onstability (FBI) in the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics Global Circulation Model, enables us, for the first time, to investigate the intimate coupling between polar turbulence electron heating and thermosphere disturbances in the context of a first principle, self consistent model. Our simulation results show that during geomagnetic storms, after taking the FBI effects into account, Joule heating is almost doubled in the E region at these locations of strong convection electric field. This increases ~6% the phase speed of traveling atmosphere disturbances at around 400 km that are launched from both hemispheres. Additional heating sources also directly produce a divergence in the zonal wind with magnitudes of 20 m/s in the lower thermosphere. However, the FBI impact on the thermosphere at F region altitudes is not so straightforward. E region anomalous electron heating in association with the FBI can change the phase speeds and magnitudes of traveling atmosphere disturbances from high latitudes in both hemispheres and consequently modify global neutral wind circulation at F region altitudes. This, in turn, can affect the neutral temperature through adiabatic compressional heating and expansive cooling by about 40 K. This study demonstrates how the ionosphere thermosphere physical processes across different temporal and spatial scales are tightly coupled together throughout the whole upper atmosphere domain.
author_names: Jing Liu

Wenbin Wang

Alan G Burns

Meers M Oppenheim

Yakov S Dimant
title: Faster Traveling Atmosphere Disturbances Caused by Polar Ionosphere Turbulence Heating
year: 2018

abstract: Perturbing the following systems (x,y) y(1 by),x(1 by))x 0, y(1 ax) x(1 ax) x 0, having a linear center with two vertical straight lines (ab0) of singularity inside the class of all piecewise polynomials of degree n, we give the estimate of the maximum number H(n) of limit cycles bifurcating from the period annulus around the center based on the argument principle and the first order averaging theory. It shows that H(n) is at least [n 2 1 bigger than the maximum number of limit cycles bifurcating from the period annulus around the linear center with two parallel straight lines of singularity in [Li Liu, 2015]
author_names: Yunfei Gao

Linping Peng

Changjian Liu
title: Bifurcation of Limit Cycles from a Class of Piecewise Smooth Systems with Two Vertical Straight Lines of Singularity
venue: Int. J. Bifurc. Chaos
year: 2017

abstract: Abstract In this work, first principle DFT calculations are carried out to identify the active center and reveal the reaction pathway on nitrogen and boron doped carbon catalysts in acetylene hydrochlorination. Various different dopant configurations including pyridine, graphitic, and pyrrolic are explored and compared. The different geometries of dopants give the distinct electronic structure, which indicate that pyridine configuration with three dopants around a vacancy, have more states around Fermi level. The adsorption of acetylene (C2H2) is predicted to be the first step of the reaction as it has much bigger binding energy than another reactant, HCl. Boron and nitrogen doping exhibit opposite effect on the charge transfer between adsorbed C2H2 and the catalyst. The curvature of tube also influences acetylene adsorption and the binding energy decreases with increasing tube diameter. Moreover, the detailed reaction pathway is revealed from the calculations. A balanced activity for C2H2 adsorption and HCl activation is required to improve catalytic performance and too strong binding of C2H2 hinders the followed steps on the pathway and cause large barrier. This work clarify the confusions facing by the metal free doped carbon catalyst and lay out solid base for the future improvements in acetylene hydrochlorination.
author_names: Sajjad Ali

Yiyang Qiu

Zan Lian

Samson O Olanrele

Guojun Lan

Yandong Li

Dang Sheng Su

Bo Li
title: Screening of active center and reactivity descriptor in acetylene hydrochlorination on metal free doped carbon catalysts from first principle calculations
venue: Applied Surface Science
year: 2019

abstract: Abstract The addition of active elements is an excellent method to improve the wettability and interfacial bonding strength between Ag and ZrB2. To quantitatively evaluate the interfacial behavior and structure stability of Ag (1 1 1)/ZrB2 (0 0 0 1) interface, the role of Ti, Zr and Hf additions in the interfacial bonding strength and electronic properties was investigated comprehensively by first principle calculations. The B terminated ZrB2 (0 0 0 1) surface is more active than the Zr terminated surface under the lower B chemical potential. For the Ag (1 1 1)/ZrB2 (0 0 0 1) interface, the interface with center site presents the largest work of adhesion W a and the lowest interfacial energy for both Zr and B terminations. The Ti, Zr and Hf additions can greatly improve the W a for Ag/ZrB2 interface (especially with the B termination) when the Ag atom in 1st layer of Ag slab is substituted by active elements. The calculation on the electronic structure shows that the ionic bonding across Ag/ZrB2 interface is further enhanced while adding the active elements due to the strong interactions between the active elements and the closest B atomics. These results provide crucial fundamental insights to enhance the wettability of Ag/ZrB2 system by the addition of active elements.
author_names: Xiangzhao Zhang

Puhao Xu

Mingfeng Zhang

Guiwu Liu

Ziwei Xu

Jian Yang

Guan-jun Qiao
title: Improving the wettability of Ag/ZrB2 system by Ti, Zr and Hf addition: An insight from first principle calculations
year: 2020

abstract: Combined liver/thoracic transplantation (cLiThTx) is a complex procedure for end stage/advanced liver and heart(H)/lung(Lu) disease. To avoid futile use of multiple organs in single recipients, results should be scrutinously analyzed. Single center cLiThTx (04/2000 12/2015) were reviewed for the following: demographics, indications, surgical technique, complications, rejection, and five year patient survival. Results are reported as median (range) Fourteen consecutive patients underwent cLiThTx: 3 cLiHTx, 10 cLiLuTx, and 1 cLiHLuTx. Recipient age was 42 years (17 63 years) Most frequent indications were cystic fibrosis (n 5) hepatopulmonary fibrosis (n 2) amyloidosis (n 2) and epithelioid hemangio endothelioma (n 2) Thoracic organs were transplanted first, except in three where LiTx preceded LuTx. In the latter, lungs were preserved by normothermic ex vivo lung perfusion. Stenting was performed for stenosis of bile duct (n 4) hepatic artery (n 2) and bronchus (n 2) Abdominal interventions were required for bleeding (n 3) evisceration (n 1) and adhesiolysis (n 1) One liver (cLiLuTx) was lost to hepatic artery thrombosis 3 months post transplant and successfully retransplanted. One patient (cLiHTx) died 4 months post transplant (myocardial infarction) Follow up was 4 years (2 months 16 years) One liver and 5 pulmonary rejections occurred, all mild and reversible. Two patients developed bronchiolitis obliterans, one is clinically well 16 years post transplant, and the other successfully retransplanted. Estimated 5 year patient survival is 90% CLiThTx is safe with excellent short /long term surgical and immunological results.
author_names: Laurens J Ceulemans

Sebastien Strypstein

Arne P Neyrinck

Stijn E Verleden

David Ruttens

Diethard Monbaliu

Paul R De Leyn

Johan Vanhaecke

Bart Meyns

Frederik Nevens

Geert M Verleden

Dirk E Van Raemdonck

Jacques Pirenne
title: Combined liver thoracic transplantation: single center experience with introduction of the 'Liver first' principle
venue: Transplant international official journal of the European Society for Organ Transplantation
year: 2016

abstract: Abstract The electronic structure and transfer characteristic of holes and electrons of GaN/ZnO heterojunction polar interface with cation vacancy were calculated by first principle. Results show that the defect levels induced by VZn in Zn N interface are made up of N 2p and O 2p states. The degeneracy of the defect levels and intrinsic CBM reduce the band gap of system. However, the defect level formed by the O 2p state may become a recombination center, which is not conducive to the separation of holes and electrons. In contrast, the defect level induced by VGa in the Ga O interface does not become a recombination center, and the larger built in electric polarization intensity in the interface can effectively prevent the recombination of holes and electrons. In addition, the spin polarization of p states weakly bound electrons induced by cation vacancy leads to spin band splitting in the conduction band, which reduces the effective mass of electron and increases the transfer velocity difference between holes and electrons, so that photogenerated holes and electrons can be effectively separated.
author_names: Congyan Li

Qingyu Hou
title: Built in magnetic electrical coupling enhances photocatalytic performance of GaN/ZnO: A first principle study
year: 2020

abstract: Abstract The interfacial properties including interfacial energy, work of adhesion and electronic structure of Al(100)/Al3Zr(100) were calculated by first principle calculations based on the density functional theory. The seven layered Al(100) slab and nine layered Al3Zr(100) slab were employed to construct the interface models. And six Al(100)/Al3Zr(100) interfaces, including Top, Bridge and Center sites for the Al and AlZr terminations, were considered to study. The interfaces with center site stacking of both terminations are the most stable as they have the largest adhesion work (Wad) The interfacial bonding characteristics is a combination of covalent and metallic bond for the AlZr terminated center site interface, but only metallic for the Al terminated center one. Under the whole range of m Z r s l a b m Z r b u l k the interfacial energy of AlZr terminated center interface is negative, which is much smaller than that of a Al and its melt (0.15J/m2) indicating that Al3Zr particle is an effective nucleant for a Al primary grains.
author_names: Tianxing Yang

Mingzhi Wei

Zongye Ding

Xiujun Han

Jianguo Li
title: First principle calculations on the Al/L12 Al3Zr heterogeneous nucleation interface
year: 2020

abstract: Surface states that have a dz 2 symmetry around the center of the surface Brillouin zone (BZ) have been regarded common in closely packed surfaces of rare earth metals. In this work, we report the electronic structure of dhcp La (0001) thin films by ultrahigh energy resolution angle resolved photoemission spectroscopy (ARPES) and first principle calculations. Our first principle analysis is based on the many body approach, therefore, density function theory (DFT) combined with dynamic mean field theory (DMFT) The experimentally observed Fermi surface topology and band structure close to the Fermi energy qualitatively agree with first principle calculations when using a renormalization factor of between 2 and 3 for the DFT bands. Photon energy dependent ARPES measurements revealed clear kZ dependence for the hole like band around the BZ center, previously regarded as a surface state. The obtained ARPES results and theoretical calculations suggest that the major bands of dhcp La (0001) near the Fermi level originate from the bulk La 5d orbits as opposed to originating from the surface states.
author_names: Xingyu Ji

Qiuyun Chen

Xinchun Lai

Li Huang

Shiyong Tan
title: Electronic structure of La (0001) thin films on W (110) studied by photoemission spectroscopy and first principle calculations
year: 2020