Error of relativistic effective core potentials for closed-shell diatomic molecules of p-block heavy and superheavy elements in DFT and TDDFT calculations.

Pseudopotentials (PP) are extensively used in electronic structure calculations, particularly for molecules containing heavy elements. Parameters in PPs are mainly determined from ab initio results, and errors of such PPs in density functional theory (DFT) calculations have been studied previously. However, PP errors on results with spin-orbit coupling and those in time-dependent DFT (TDDFT) calculations have not been reported previously. In this work, we investigate the error of the small-core energy-consistent Stuttgart/Koln pseudopotentials in DFT and TDDFT calculations with and without spin-orbit coupling. Ground state bond lengths, harmonic frequencies, dissociation energies, and vertical excitation energies for a series of closed-shell diatomic heavy and superheavy p-block molecules are calculated using several popular exchange-correlation functionals. PP errors are estimated by comparing with results using the all-electron Dirac-Coulomb (-Gaunt) Hamiltonian. Our results show that the difference between ground state properties and most excitation energies in scalar-relativistic calculations with the PP and those of all-electron calculations is quite small. This difference becomes somewhat larger when spin-orbit coupling (SOC) is present, especially for properties that are affected by SOC to some extent. In addition, the errors of the PPs are insensitive to the employed exchange-correlation functionals in most cases. Our results indicate that reasonable DFT and TDDFT results can be obtained using the small-core energy-consistent Stuttgart/Koln pseudopotentials for heavy and super-heavy p-block molecules.

Design and characterization of a varifocal camera system with an extended depth of field and focal range.

This paper presents the design and characterization of a compact and affordable varifocal camera system. With its entrance pupil located in front as the first element for easy access, the camera system offers a working F/# as low as 2, is capable of focusing across a wide depth range from optical infinity to as close as 4 diopters through an electrically tunable lens, and maintains nearly constant angular magnification through the focus range by placing the focusing element at proximity to the entrance pupil. These unique features can find a myriad of applications such as image-based head-mounted display calibration and extended depth of field (EDOF) imaging. The paper further demonstrates a single-shot EDOF imaging function by utilizing its property of nearly constant angular magnification through focus scanning.

Intermediate Hamiltonian Fock-space coupled-cluster theory for excitation energies, double ionization potentials, and double electron attachments with spin-orbit coupling.

The intermediate Hamiltonian Fock-space coupled-cluster methods at the singles and doubles level (IHFSCCSD) for excitation energies in the (1p, 1h) sector, double ionization potentials in the (0p, 2h) sector, and double electron attachments in the (2p, 0h) sector of the Fock space are implemented based on the CCSD method with spin-orbit coupling (SOC) included in the post-Hartree-Fock treatment using a closed-shell reference in this work. The active space is chosen to contain those orbitals that have the largest contribution to principal ionized or electron-attached states obtained from the equation-of-motion coupled-cluster calculations. Both time-reversal symmetry and spatial symmetry are exploited in the implementation. Our results show that the accuracy of IHFSCCSD results is closely related to the active space, and the sufficiency of the active space can be assessed from the percentage of transitions within the active space. In addition, unreasonable results may be encountered when the ionized or electron-attached states with a somewhat larger contribution from double excitations are included to determine the active space and cluster operators in the (0p, 1h) or (1p, 0h) sector of the Fock space. A larger active space may be required to describe SO splitting reliably than that in the scalar-relativistic calculations in some cases. The IHFSCCSD method with SOC developed in this work can provide reliable results for heavy-element systems when a sufficient active space built upon the principal ionization potential/electron affinity states is adopted.

Interlayer Exciton Transport in MoSe2/WSe2 Heterostructures.

A moiré superlattice formed by stacking two lattice mismatched transition metal dichalcogenide monolayers, functions as a diffusion barrier that affects the energy transport and dynamics of interlayer excitons (electron and hole spatially concentrated in different monolayers). In this work, we experimentally quantify the diffusion barrier experienced by interlayer excitons in hexagonal boron nitride-encapsulated molybdenum diselenide/tungsten diselenide (MoSe2/WSe2) heterostructures with different twist angles. We observe the localization of interlayer excitons at low temperature and the temperature-activated diffusivity as a function of twist angle and hence attribute it to the deep periodic potentials arising from the moiré superlattice. We further support the observations with theoretical calculations, Monte Carlo simulations, and a three-level model that represents the exciton dynamics at various temperatures.

Modulation-format-independent OSNR monitoring insensitive to cascaded filtering effects by low-cost coherent receptions and RF power measurements.

Optical signal-to-noise ratio (OSNR) monitoring is indispensable for ensuring robust and flexible optical networks that provide failure diagnosis, dynamic lightpath provisioning and modulation format adaptation. We propose and experimentally demonstrate a low-cost, modulation-format-independent OSNR monitoring scheme utilizing reduced-complexity coherent receptions, electrical filtering and radio frequency (RF) power measurements. By measuring the RF power of the coherently received baseband signals at three different frequency components, the proposed OSNR monitor is also insensitive to spectral narrowing induced by cascaded wavelength selective switches (WSSs). We experimentally demonstrate accurate data-format-transparent and filtering-effect-insensitive OSNR monitoring for 25-Gbaud dual-polarization (DP-) transmissions with QPSK, 16-QAM and 64-QAM signals over various distances with different amount of filtering effects by cascaded WSSs. We further characterize the influence of different system parameters, such as the bandwidth of the electrical low-pass filter, the laser frequency offset and laser linewidth on the accuracy of the proposed OSNR monitor. The robustness of the proposed OSNR monitoring scheme to fiber nonlinearities, calibration parameter mismatches and variations of WSS parameters are also investigated.

[Correlation between cystatin C and properties and features of coronary plague].

OBJECTIVE: To explore the correlation between cystatin C (Cys C) and properties and features of coronary plague using 256-slice coronary computed tomography angiography (CTA). METHODS: From January 2013 to October 2013, a total of 184 patients with suspected coronary artery disease undergoing CTA for coronary artery lesions were enrolled. Based on the results of cystatin C levels, they were divided into normal Cys C concentration group ( ≤ 0.95 mg/L) and high Cys C concentration group (>0.95 mg/L). Based on the results of CTA, they were divided into single-vessel, 2-vessel and 3-vessel groups according to the number of diseased coronary arteries. And they were divided into mild stenosis (<50%), moderate stenosis ( ≥ 50%, <75%) and severe stenosis ( ≥ 75%) groups according to the severity of coronary artery disease. The Hounsfield units were used to determine the soft, fibrous and calcified plaques for assessing the relationship between cystatin C levels and narrow severity score, pathological changes limits, plague properties. RESULTS: There were 95 with normal concentrations of Cys C and 89 with high concentrations of Cys C. A total of 1 112 plaques were detected and those with high concentrations of Cys C showed a higher proportion of non-calcified plaque (13.5% vs 8.8%, P < 0.01) compared with normal group. The proportion of those with 1-vessel disease was lower (22.5% vs 37.9%, P < 0.05) but 3-vessel disease higher (48.3% vs 33.7%, P < 0.05) than in normal group. Multiple Logistic regression analysis revealed that high Cys C was a significant risk factor for multi-vessel disease (OR = 17.483, 95%CI:2.218-143.627; P < 0.01). CONCLUSION: For patients with coronary artery lesions, a high level of Cys C may be associated with severity of coronary atherosclerosis and plaque instability.