Accuracy of Localized Resolution of the Identity in Periodic Hybrid Functional Calculations with Numerical Atomic Orbitals

We present an implementation of hybrid density functional approximations for periodic systems within a pseudopotential-based, numerical atomic orbital (NAO) framework. The two-electron Coulomb repulsion integrals (ERIs) are evaluated using the localized resolution-of-the-identity (LRI) approximation. The accuracy of the LRI approximation is benchmarked unambiguously against independent reference results obtained via a computational scheme whereby the ERIs are accurately evaluated by expanding the products of NAOs in terms of plane waves. An alternative strategy for constructing auxiliary basis sets is proposed, and its accuracy is assessed and compared to the previously used procedure. Finally, the reliability of our algorithm and implementation is benchmarked against other established implementations within different numerical frameworks in terms of the calculated band gap values of a set of semiconductors and insulators

Real-Time, Time-Dependent Density Functional Theory Study on Photoinduced Isomerizations of Azobenzene Under a Light Field

The trans to cis photoisomerization of azobenzene and its reverse (i.e., the cis to trans) processes are studied using real-time propagation time-dependent density functional theory combined with molecular dynamics for ions. We show that the wavelength of the applied laser may significantly affect the transition process. The simulations also show that the photon-excited electrons play essential roles in the isomerization processes, in which the hot electrons couple to phonon modes that drive the transitions

Real-Time, Time-Dependent Density Functional Theory Study on Photoinduced Isomerizations of Azobenzene Under a Light Field

The trans to cis photoisomerization of azobenzene and its reverse (i.e., the cis to trans) processes are studied using real-time propagation time-dependent density functional theory combined with molecular dynamics for ions. We show that the wavelength of the applied laser may significantly affect the transition process. The simulations also show that the photon-excited electrons play essential roles in the isomerization processes, in which the hot electrons couple to phonon modes that drive the transitions

All-optical spatio-temporal metrology for isolated attosecond pulses

Characterizing an isolated attosecond pulse (IAP) is essential for its potential applications. A complete characterization of an IAP ultimately requires the determination of its electric field in both time and space domains. However, previous methods, like the widely-used RABBITT and attosecond streaking, only measure the temporal profile of the attosecond pulse. Here we demonstrate an all-optical method for the measurement of the space-time properties of an IAP. By introducing a non-collinear perturbing pulse to the driving field, the process of IAP generation is modified both spatially and temporally, manifesting as a spatial and a frequency modulation in the harmonic spectrum. By using a FROG-like retrieval method, the spatio-spectral phases of the harmonic spectrum are faithfully extracted from the induced spatio-spectral modulations, which allows a thoroughgoing characterization of the IAP in both time and space. With this method, the spatio-temporal structures of the IAP generated in a two-color driving field in both the near- and far-field are fully reconstructed, from which a weak spatio-temporal coupling in the IAP generation is revealed. Our approach overcomes the limitation in the temporal measurement in conventional in situ scheme, providing a reliable and holistic metrology for IAP characterization

All-optical measurement of high-order fractional molecular echoes by high-order harmonic generation

An all-optical measurement of high-order fractional molecular echoes is demonstrated by using high-order harmonic generation (HHG). Excited by a pair of time-delayed short laser pulses, the signatures of full and high order fractional (1/2 and 1/3) alignment echoes are observed in the HHG signals measured from CO2 molecules at various time delays of the probe pulse. By increasing the time delay of the pump pulses, much higher order fractional (1/4) alignment echo is also observed in N2O molecules. With an analytic model based on the impulsive approximation, the spatiotemporal dynamics of the echo process are retrieved from the experiment. Compared to the typical molecular alignment revivals, high-order fractional molecular echoes are demonstrated to dephase more rapidly, which will open a new route towards the ultrashort-time measurement. The proposed HHG method paves an efficient way for accessing the high-order fractional echoes in molecules

Excited Oxidized-Carbon Nanodots Induced by Ozone from Low-Temperature Plasma to Initiate Strong Chemiluminescence for Fast Discrimination of Metal Ions

Carbon nanodots (C-dots) are recently well examined due to the emissions with color-tuning and nonblinking properties, while more studies are still needed for the appropriate understanding and application of distinct emissions. In this work, we found the emission of chemiluminescence (CL) by introducing low-temperature plasma (LTP) into C-dots solutions without any reagent added, whose intensity was affected by the presence of different metal ions. Based on both experimental data and theoretical calculations, we found with the ozonation by ozone from LTP, excited oxidized-C-dots would be generated with the addition of ozone onto the conjugated double bonds of C-dots, and these excited species could directly initiate strong CL combining with the deactivation of excited species to the ground state. Significantly, the cross-reactive CL signals were obtained from different kinds of C-dots with the presence of different metal ions. Therefore, a new sensor array (electronic tongue) composed of five different C-dots was designed for fast discrimination of metal ions, which achieved the accurate discrimination of 13 kinds of metal ions in pure water and real samples. It exhibited good reproducibility and sensitivity, which can be used for the quantitative analysis of metal ions such as showing a linear range from 4 × 10^–7 to 6 × 10^–5 mol·L^–1 (<i>R</i>² > 0.99) for Fe³⁺ with a detection limit of 2.5 × 10^–7 mol·L^–1. This work not only provides a novel finding of CL from C-dots revealing explicit relationship between structures and CL properties, but also realizes the fast discrimination of metal ions, showing potentials in environmental monitoring and quality identifications

Molecular rotation movie filmed with high-harmonic generation

Direct imaging of molecular dynamics is a long-standing goal in physics and chemistry. As an emerging tool, high-harmonic spectroscopy (HHS) enables accessing molecular dynamics on femtosecond to attosecond time scales. However, decoding information from the harmonic signals is usually painstaking due to the coherent nature of high-harmonic generation (HHG). Here we show that this obstacle can be effectively overcome by exploiting machine learning in HHS. Combining the machine learning with an angle-resolved HHS method, we demonstrate that the rich dynamics of molecular rotational wave packet is fully reconstructed from the angular distributions of HHG measured at various time delays of the probe pulse. The experimental retrievals are in good agreement with the numerical simulations. These findings provide a comprehensive picture of molecular rotation in space and time which will facilitate the development of related researches on molecular dynamics imaging

TNSPackage: A Fortran2003 library designed for tensor network state methods

Recently, the tensor network states (TNS) methods have proven to be very powerful tools to investigate the strongly correlated many-particle physics in one and two dimensions. The implementation of TNS methods depends heavily on the operations of tensors, including contraction, permutation, reshaping tensors, SVD and so on. Unfortunately, the most popular computer languages for scientific computation, such as Fortran and C/C++ do not have a standard library for such operations, and therefore make the coding of TNS very tedious. We develop a Fortran2003 package that includes all kinds of basic tensor operations designed for TNS. It is user-friendly and flexible for different forms of TNS, and therefore greatly simplifies the coding work for the TNS methods

Tomography of asymmetric molecular orbitals with one-color inhomogeneous field

We demonstrate to image asymmetric molecular orbitals via high-order harmonic generation in a one-color inhomogeneous field. Due to the broken inversion symmetry of the inhomogeneous field in space, the returning electrons with energy in a broad range can be forced to recollide from only one direction for all the orientation angles of molecules, which therefore can be used to reconstruct asymmetric molecular orbitals. Following the procedure of molecular orbital tomography, the highest occupied molecular orbital of CO is satisfactorily reconstructed with high-order harmonic spectra driven by the inhomogeneous field. This scheme is helpful to relax the requirement of laser conditions and also applicable to other asymmetric molecules