Time-dependent Density Functional Perturbation Theory Research Articles

From Bulk to one-dimensional MoS2 nanochains: evolution of electronic, mechanical, and optical properties

We theoretically investigate the stability of a MoS2 nanochain, reporting its electronic, mechanical, and optical properties. The nanochain presents a semiconductor structure with a minute band gap of 67m eV compared to the larger gap bulk and monolayer structures. It is more malleable, enduring a maximum compressive (tensile) strain of 6% (6.5%). It is dynamically stable, showing no negative frequencies along its Brillouin zone (BZ) path. The nanochain is thermally stable at 300K, making it possible to synthesize as a freestanding structure. The optical properties of the bulk, monolayer, and 1D MoS2 materials are evaluated using the time-dependent density functional perturbation theory (TDDFPT) and compared to those determined via the independent particle approximation (IPA). Along the nanochain’s periodic x direction, the reflectivity retains a maximum value of ∼68% in the infrared (IR) region. Furthermore, its optical conductivity also exhibits a peak within the IR regime. These two features make such nanochains suitable as coating materials in applications involving infrared radiation or can even be exploited as conductive substrates in near-IR devices.

Demagnetizing Ferromagnetic Catalysts to the Sabatier Optimal of Haber-Bosch Process.

Achieving the Sabatier optimal of a chemical reaction has been the central topic in heterogeneous catalysis for a century. However, this ultimate goal was greatly hindered in previous catalyst design strategies since the active sites indeed changed. Fortunately, the magneto-catalytic effect (MCE) provides a promising solution to this long-standing challenge. Recent research suggests that the performance of ferromagnetic catalysts is capable to be promoted without changing its chemical structure. Herein, we use time-dependent density functional perturbation theory (TDDFPT) calculations to elucidate that a partially demagnetized (DM) ferromagnet could be a Sabatier optimal catalyst. Using ammonia synthesis as the model reaction, we determined the activity of Cobalt at each DM state by including the magnetic thermal excitations via magnon analysis, making the 55% DM Co to the genuine Sabatier optimal. As an essential but underexcavated phenomenon in heterogeneous catalysis, the MCE will open a new avenue to design high-performance catalysts.

Ab initio study of spin fluctuations in the itinerant kagome magnet FeSn

Kagome antiferromagnetic metal FeSn has become an attracting platform for the exploration of novel electronic states, such as topological Dirac states and the formation of flat bands by localized electrons. Apart from the electronic properties, Dirac magnons and flat magnon bands have also been proposed by applying simplified Heisenberg models to kagome magnetic systems.Inelastic neutron scattering studies on FeSn found well defined magnon dispersions at low energies,but magnons at high energies are strongly dampled, which can not be explained by localized spin models. In this paper, we utilize both linear spin wave theory and time-dependent density functional perturbation theory to investigate spin fluctuations of FeSn. Through the comparison of calculated spin wave spectra and Stoner continuum, we explicitly show that the damping of magnons at high energies are due to the Landau damping, and the appearance of high energy optical-magnon like branches at the M and K point are resulted by relatively low Stoner excitation intensity at those regions.

TurboMagnon – A code for the simulation of spin-wave spectra using the Liouville-Lanczos approach to time-dependent density-functional perturbation theory

We introduce turboMagnon, an implementation of the Liouville-Lanczos approach to linearized time-dependent density-functional theory, designed to simulate spin-wave spectra in solid-state materials. The code is based on the noncollinear spin-polarized framework and the self-consistent inclusion of spin-orbit coupling that allow to model complex magnetic excitations. The spin susceptibility matrix is computed using the Lanczos recursion algorithm that is implemented in two flavors - the non-Hermitian and the pseudo-Hermitian one. turboMagnon is open-source software distributed under the terms of the GPL as a component of Quantum ESPRESSO. As with other components, turboMagnon is optimized to run on massively parallel architectures using native mathematical libraries (LAPACK and FFTW) and a hierarchy of custom parallelization layers built on top of MPI. The effectiveness of the code is showcased by computing magnon dispersions for the CrI3 monolayer, and the importance of the spin-orbit coupling is discussed. Program summaryProgram title:turboMagnonCPC Library link to program files:https://doi.org/10.17632/6zxwzv5dt4.1Licensing provisions: GNU General Public License V 2.0Programming language: Fortran 95External routines:turboMagnon is a tightly integrated component of the Quantum ESPRESSO distribution and requires the standard libraries linked by it: BLAS, LAPACK, FFTW, MPI.Nature of problem: Calculation of the spin-wave spectra for solid-state materials.Solution method: The spin susceptibility matrix of a periodic system is expressed in terms of the resolvent of its Liouvillian superoperator within time-dependent density-functional perturbation theory. It is calculated using non-Hermitian or pseudo-Hermitian variants of the Lanczos recursion scheme, whose implementation does not require the calculation of empty electronic states. Norm-conserving pseudopotentials are used in conjunction with plane-wave basis sets and periodic boundary conditions. Relativistic effects (spin-orbit coupling) can be included in calculations.Additional comments including restrictions and unusual features: Linear-response regime only. Collinear spin-polarized formalism is not supported, only noncollinear spin-polarized case can be used. Adiabatic LSDA exchange-correlation functionals only (no GGA, no meta-GGA, no hybrid functionals, no Hubbard U, etc.). No ultrasoft and projector-augmented-wave pseudopotentials. No symmetry.Empty states are not used, nor even calculated. Three Lanczos recursions give access to the whole spectrum of magnetic excitations at fixed transferred momentum; one Lanczos recursion is enough for a specific orientation of the magnetic field and the ground-state magnetization of the system.The distribution file of this program can be downloaded from the Quantum ESPRESSO website: http://www.quantum-espresso.org/, and the development version of this program can be downloaded via Git from the GitLab website: https://gitlab.com/QEF/q-e. Interactions with end users of the turboMagnon code happen via a mailing-list forum of Quantum ESPRESSO: https://www.quantum-espresso.org/forum. Documentation of the turboMagnon code is tightly coupled with the code and is done via standard code comments.

First-principles theory of infrared vibrational spectroscopy of metals and semimetals: Application to graphite

We develop an ab initio method to simulate the infrared vibrational response of metallic systems in the framework of time-dependent density functional perturbation theory. By introducing a generalized frequency-dependent Born effective charge tensor, we show that phonon peaks in the reflectivity of metals can be always described by a Fano function, whose shape is determined by the complex nature of the frequency-dependent effective charges and electronic dielectric tensor. The IR vibrational properties of graphite, chosen as a representative test case to benchmark our method, are found to be accurately reproduced. Our approach offers a first-principle scheme for the prediction and understanding of IR reflectance spectra of metals, that may represent one of the few available tools of investigation of these materials when subjected to extremely high-pressure conditions.

Band structure and absorption spectra of NH4XI3 (X = Pb, Mg) based hybrid Perovskite for UV ray protector and electrochromic materials applications

Modeling Perovskite materials and tuning their properties by monovalent or divalent cations substitution produce several choice Perovskite compounds, studied extensively to improve the power conversion efficiency, reduce toxicity, and enhance stability. We modeled NH4PbI3 and NH4MgI3 from the parent compound CH3NH3PbI3, by replacing the monovalent CH3NH3+ with NH4+ and the divalent Pb atom with Mg. In this study, the electronic band structure, as well as the electronic bandgaps, were calculated using the Perdew-Burke-Enzenhoff (PBE) and Perdew-Burke-Enzenhoff for solid (PBEsol) exchange-correlation functionals of the Density-functional Theory (DFT) and GW quasiparticle method of the Many-Body Perturbation Theory (MBPT). Similarly, we used Time-Dependent Density Functional Perturbation Theory (TDDFPT) and the solution of the Bethe-Salpeter equation (BSE) of the Many-Body Perturbation Theory to determine the real and imaginary dielectric tensors with and without spin-orbit coupling (SOC). Direct bandgaps at R high symmetry point were reported for NH4PbI3, while NH4MgI3 showed indirect bandgaps at Γ→R high symmetry points with lower bandgaps compared to NH4PbI3. The projected density of state around the Fermi level reveals that the iodine (I) p orbital is most responsible for the valence band in both NH4PbI3 and NH4MgI3, while the Lead (Pb) p orbital and the Magnesium (Mg) s orbitals, show the most prominent contribution to the Conduction bands. Similar Optical spectra were achieved with BSE-SOC, TDDFPT, and TDDFPT-SOC for NH4PbI3 without the absorption onsets, while NH4PbI3 predicts higher values of absorbance and absorption coefficient compared to NH4MgI3 which predict lower reflectivity and higher transmittance. Both compounds show maximum absorption coefficient in the order of 105 in the ultraviolet region like CH3NH3PbI3 and silicon. Therefore, we suggest that NH4PbI3 will be useful as solar cell absorber and UV ray protector, while NH4MgI3 would have more applications in the production of electrochromic materials.

Electron energy loss spectroscopy of bulk gold with ultrasoft pseudopotentials and the Liouville-Lanczos method

The implementation of ultrasoft pseudopotentials into time-dependent density-functional perturbation theory is detailed for both the Sternheimer approach and the Liouville-Lanczos (LL) method, and equations are presented in the scalar relativistic approximation for periodic solids with finite momentum transfer q. The LL method is applied to calculations of the electron energy loss (EEL) spectrum of face-centered cubic bulk Au both at vanishing and finite q. Our study reveals the richness of the physics underlying the various contributions to the density fluctuation in gold. In particular, our calculations suggest the existence in gold of two quasi-separate 5d and 6s electron gasses, each one oscillating with its own frequency at resp. 5.1 eV and 10.2 eV. We find that the contribution near 2.2 eV comes from 5d to 6s interband transitions modified by the intraband contribution to the real part of the dielectric function, which we call a mixed excitation.

A theoretical study of the structural and electronic properties of poly(9-vinylcarbazole) interacting with small-diameter single-walled carbon nanotubes

Density functional perturbation theory (DFPT) and time-dependent density functional perturbation theory (TDDFPT) calculations were employed to study the molecular and electronic structures, linear and nonlinear optical properties, optical phonon modes and vibrational properties of the interaction of poly(9-vinylcarbazole) (PVK)–small-diameter single-walled carbon nanotube (SWCNT) composites. Our calculations show that the chemical connection between PVK and SWCNTs is only through the relatively weak [Formula: see text]–[Formula: see text] and [Formula: see text]–H bonds. PVK and SWCNTs have different electron accepting abilities and we believe this is the major factor responsible for the charge transfer processes we observe in the calculations. We notice an increase in polarizability value from 152 a.u. (PVK) to 517 a.u. (PVK–SWCNTs), making the PVK–SWCNT composite an ideal model for applications such as mechanical and optoelectronics. Also, the result of our calculations under the time-dependent density functional perturbation theory hinges on the idea that the large value of the polarizability calculated for our composite model is an attribute which can be inferred to processes of charge transfer. Our finding corroborates the fact that non-covalent functionalization is one of the effective chemical methods by which the nonlinear optical response properties of PVK–SWCNT composite may be enhanced.

SternheimerGW: A program for calculating [formula omitted] quasiparticle band structures and spectral functions without unoccupied states

The SternheimerGW software uses time-dependent density-functional perturbation theory to evaluate GW quasiparticle band structures and spectral functions for solids. Both the Green’s function G and the screened Coulomb interaction W are obtained by solving linear Sternheimer equations, thus overcoming the need for a summation over unoccupied states. The code targets the calculation of accurate spectral properties by convoluting G and W using a full frequency integration. The linear response approach allows users to evaluate the spectral function at arbitrary electron wavevectors, which is particularly useful for indirect band gap semiconductors and for simulations of angle-resolved photoelectron spectra. The software is parallelized efficiently, integrates with version 6.3 of Quantum Espresso, and is continuously monitored for stability using a test farm. Program summaryProgram Title:SternheimerGWProgram Files doi:http://dx.doi.org/10.17632/7ywzjng9t5.1Licensing provisions: GNU General Public License v3.0Programming language: Fortran 2003Nature of problem: The lack of the exchange–correlation discontinuity in density-functional theory (DFT) leads to a systematic underestimation of the band gap between conduction and valence states. Many-body perturbation theory in the GW approximation provides an effective solution to this problem, as well as other limitations faced by DFT in the description of electronic excitations. However, the GW method comes with its own set of limitations: (i) The perturbation of the system is typically expressed in terms of the unoccupied states, and achieving numerical convergence with respect to these states is often cumbersome. Since the underlying DFT codes rely only on the occupied states, their default behavior is often ill-suited to provide a sufficient amount of empty states. Combined with the large number of parameters that need to be converged, this limits the use of GW codes by non-expert users and automatic scripts. (ii) Currently, GW codes require that a homogeneous k-point mesh is used in the calculation. Hence, features close to the band edges are often only accessible via prohibitively expensive dense k-point meshes or interpolation techniques. (iii) To evaluate the frequency convolution of the Green’s function G and the screened Coulomb interaction W, many current GW calculations rely on approximations such as the plasmon-pole approximation, the analytic continuation, or the contour deformation. The relative merits and accuracy of the various approximations are not fully understood.Solution method: In SternheimerGW, we address (i) by replacing the summation over unoccupied states with a linear response equation. The solution depends on the occupied states only, and it employs linear response algorithms already provided by the Quantum ESPRESSO suite to compute phonons and related properties. As an additional benefit, transforming the problem in a linear response equation removes the restriction to homogeneous k-point meshes (ii), so that the GW self-energy for any arbitrary point can be evaluated. Finally (iii), we provide the possibility to perform a full frequency convolution along the real frequency axis. This feature can serve as a benchmark for approximate integrations using models or analytic continuation.

Unraveling the Stable Phase, High Absorption Coefficient, Optical and Mechanical Properties of Hybrid Perovskite CH3NH3PbxMg1–xI3: Density Functional Approach

The quest for materials with optimum photovoltaic conversion efficiency leads to the discovery of CH3NH3PbI3, which has shown exciting improvement in power conversion efficiency over the silicon-based technology. This research uses PBEsol–KJPAW and PBE-NC functionals as implemented in Density Functional Theory to study the effects of Mg doping in CH3NH3PbxMg1–xI3 solar cell absorber for x = 0, 0.25, 0.50, 0.75, 1. The Absorption spectrum is computed with Time-Dependent Density Functional Perturbation Theory while the optical gap is calculated by fitting the absorption edge with the Tauc direct and indirect allowed transition. The ground state energy and lattice parameters of CH3NH3PbxMg1–xI3 in its cubic, tetragonal and orthorhombic crystal structures were calculated to determine its equilibrium structure, which appears to be simple cubic for all the compounds of interest. Electronic band gaps were calculated to be in the range 1.16–2.12 eV, suggesting an excellent power conversion efficiency according to the Shockley–Queisser efficiency limit, but the optical gaps extrapolated from the absorption spectrum is larger than the calculated DFT band gap, as a result of underestimation of calculated DFT band gap in Mg-doped CH3NH3PbI3. CH3NH3PbxMg1–xI3 is found to be brittle, moderately incompressible with Vickers hardness in the range of 6.776–9.153 GPa. The brittleness, incompressibility, and hardness all increase with Mg concentration. The amount of solar radiation absorbed and the percentage reflectivity depends on the concentration of Pb while transmitted solar irradiation increase with Mg concentration, these suggest that MAPbI3 may have better power conversion efficiency compared to Mg-doped MAPbI3, but Mg doping will reduce the toxic effect of Pb and produce much more power conversion efficiency than the silicon-based solar cell.

Simulation of electron energy loss spectra with the turboEELS and thermo_pw codes

For some materials like noble metals, electron energy loss spectra have a complex structure that makes them difficult to analyze without the help of ab initio calculations. Various theoretical approaches can be used for this purpose, among which the time-dependent density functional perturbation theory (TDDFPT) which has been widely used to study plasmons in a number of bulk and surface systems. In the present paper we present a comparison of the results and performance of two different numerical implementations of TDDFPT: the Sternheimer and Liouville-Lanczos methods. The former approach is implemented in the thermo_pw module and the latter one in the turboEELS code of the QUANTUM ESPRESSO package for electronic structure calculations. In the present paper a comparison is made for bulk bismuth, a semimetal, taking into account spin-orbit coupling, as well as for bulk gold, a noble metal. We show that for these two examples, both codes gives identical results and the turboEELS code has a better performance than the thermo_pw code, and point out in which cases the usage of thermo_pw alone or of both codes can be advantageous.

Spin dynamics from time-dependent density functional perturbation theory

We present a new method to model spin-wave excitations in magnetic solids, based on the Liouville-Lanczos approach to time-dependent density functional perturbation theory. This method avoids computationally expensive sums over empty states and naturally deals with the coupling between spin and charge fluctuations, without ever explicitly computing charge-density susceptibilities. Spin-wave excitations are obtained with one Lanczos chain per magnon wave-number and polarization, avoiding the solution of the linear-response problem for every individual value of frequency, as other state-of-the-art approaches do. Our method is validated by computing magnon dispersions in bulk Fe and Ni, resulting in agreement with previous theoretical studies in both cases, and with experiment in the case of Fe. The disagreement in the case of Ni is also comparable with that of previous computations.

Large-scale ab initio calculations of Raman scattering spectra within time-dependent density functional perturbation theory.

We develop an ab initio approach for large-scale Raman scattering spectra simulations based on time-dependent density functional theory in conjunction with the plane-wave pseudopotential method at the Gamma point. A Lagrangian functional is introduced to analytically compute the first-order derivatives of the frequency dependent polarizability with respect to nuclear coordinates. The computational effort of Raman intensities required by our method is reduced by one power of system size compared to that required for phonon frequency calculations. The method is validated for several molecular and solid systems including CH4, C2H2, C6H6, C60, bulk Si, and boron doped Si crystal and exhibits excellent agreements with the experimental Raman spectra. We show that the method yields a computational scaling of Ne2, with Ne ranging from 32 to 4000 electrons, opening doors for many large-scale Raman spectra computations that are beyond the reach of previous approaches.

Ab initio calculation of spin fluctuation spectra using time-dependent density functional perturbation theory, plane waves, and pseudopotentials

We present an implementation of time-dependent density functional perturbation theory for spin fluctuations, based on planewaves and pseudopotentials. We compute the dynamic spin susceptibility self-consistently by solving the time-dependent Sternheimer equation, within the adiabatic local density approximation to the exchange and correlation kernel. We demonstrate our implementation by calculating the spin susceptibility of representative elemental transition metals, namely bcc Fe, fcc Ni and bcc Cr. The calculated magnon dispersion relations of Fe and Ni are in agreement with previous work. The calculated spin susceptibility of Cr exhibits a soft-paramagnon instability, indicating the tendency of the Cr spins to condense in a incommensurate spin density wave phase, in agreement with experiment.

Analysis of Localized Surface Plasmon Resonances in Spherical Jellium Clusters and Their Assemblies

Due to multiple possible applications of physico-chemical properties of plasmonic metal nanoparticles and particle systems, there is high interest to understand the mechanisms that underlie the birth of localized surface plasmon resonance (LSPR). Here we studied the birth of the LSPR in spherical jellium clusters with the density of sodium and with 8, 20, 34, 40, 58, 92, 138, and 186 electrons, by using the linear response time-dependent density functional theory (lr-TDDFT). The coupling of the individual plasmon resonances in dimer, trimer, tetramer, and hexamer cluster assemblies consisting of the 8-electron cluster was also studied. The Kohn-Sham electron-hole transitions contributing to the absorption peaks were analyzed using time dependent density functional perturbation theory (TD-DFPT) and visualized using the transition contribution map (TCM) analysis. The plasmonicity of an absorption peak was analyzed by examining the number of the e-h transitions contributing to it, the relative strengths of t...

Resonance enhanced multiphoton ionization − time of flight (REMPI-TOF) detection of Br ( 2 P j ) atoms in the photodissociation of 4-bromo-2,3,5,6-tetrafluoropyridine at 234 nm: Effect of low-lying πσ* states

Abstract The photodissociation dynamics of 4-bromo-2,3,5,6-tetrafluoropyridine (BTFP) have been studied in a supersonic molecular beam around 234 nm, which prepares the molecule in its ππ* state. The dynamics of the C Br bond dissociation have been investigated using resonance-enhanced multiphoton ionization coupled with time-of-flight mass spectrometer (REMPI-TOFMS) by detecting the nascent spin orbit states of the primary bromine atoms, namely, Br (2P3/2) and Br*(2P1/2). State specific polarization dependent TOF profiles were obtained, from which the translational energy distributions and recoil anisotropy parameters, βi, were extracted using forward convolution method. A strong polarization dependence of TOF profiles suggests anisotropic distributions of the Br and Br* fragments. Two components, namely, the fast and the slow, are observed in the translational energy distribution of Br and Br* atoms, formed from different potential energy surfaces. The average translational energies released into the Br and Br* channels for the fast component are 17.3 ± 2.0 and 11.1 ± 2.0 kcal/mol, respectively. Similarly, for the slow component, the average translational energies imparted into the Br and Br* channels are 2.6 ± 1.0 and 1.5 ± 1.0 kcal/mol, respectively. The relative quantum yields of Br and Br* are 0.87 ± 0.15 and 0.13 ± 0.06. The anisotropy parameters for Br and Br* are characterized by a similar value of 0.60 ± 0.05. The energy partitioning into the translational modes is interpreted with the help of various models. The experimental studies revealing the nature of translational energies distribution for Br and Br* and its average value along with the theoretical calculations employing Time-Dependent Density Functional Theory (TD-DFT) and Multi Configuration Quasi Degenerate second order Perturbation Theory (MCQDPT2) suggest that the initially prepared ππ* state crosses over to a nearby σ* repulsive state along the C Br bond, mainly, πσ* state from where the dissociation takes place. The results also indicate the process of fast internal conversion to ground state from the initially prepared ππ* state, which eventually forms slow Br atoms after C-Br bond dissociation process on the ground state. During the course of experiments, the absorption spectrum was also obtained with its absolute absorption cross section. Non-adiabatic curve crossing plays an important role in the C Br bond dissociation of BTFP.

Ab initiostudy of electron energy loss spectra of bulk bismuth up to 100 eV

The dynamical charge-density response of bulk bismuth has been studied within time-dependent density functional perturbation theory, explicitly accounting for spin-orbit coupling. The use of the Liouville-Lanczos approach allows us to calculate electron energy loss spectra for excitation energies as large as 100 eV. Effects of 5d semicore electronic states, spin-orbit coupling, exchange and correlation, local fields, and anisotropy are thoroughly investigated. The account of the 5d states in the calculation turns out to be crucial to correctly describe the loss spectra above 10 eV and, in particular, the position and shape of the bulk-plasmon peak at 14.0 eV at vanishing transferred momentum. Our calculations reveal the presence of interband transitions at 16.3 eV, which had never been discussed before. The origin of the peak at 5.8 eV is revisited as due to mixed interband and collective excitations. Finally, our study supplements the lack of experiments at finite transferred momenta.

TurboEELS—A code for the simulation of the electron energy loss and inelastic X-ray scattering spectra using the Liouville–Lanczos approach to time-dependent density-functional perturbation theory

We introduce turboEELS, an implementation of the Liouville–Lanczos approach to linearized time-dependent density-functional theory, designed to simulate electron energy loss and inelastic X-ray scattering spectra in periodic solids. turboEELS is open-source software distributed under the terms of the GPL as a component of Quantum ESPRESSO. As with other components, turboEELS is optimized to run on a variety of different platforms, from laptops to massively parallel architectures, using native mathematical libraries (LAPACK and FFTW) and a hierarchy of custom parallelization layers built on top of MPI. Program summaryProgram title: turboEELSCatalogue identifier: AEXB_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEXB_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: GNU General Public License V 2.0No. of lines in distributed program, including test data, etc.: 1371515No. of bytes in distributed program, including test data, etc.: 37355712Distribution format: tar.gzProgramming language: Fortran 95.Computer: Any computer architecture.Operating system: GNU/Linux, AIX, IRIX, Mac OS X, and other UNIX-like OS’s.Classification: 7.2.External routines: turboEELS is a tightly integrated component of the Quantum ESPRESSO distribution and requires the standard libraries linked by it: BLAS, LAPACK, FFTW, MPI.Nature of problem: Calculation of the electron energy loss and inelastic X-ray scattering spectra of periodic solids.Solution method: The charge-density susceptibility of a periodic system is expressed in terms of the resolvent of its Liouvillian superoperator within time-dependent density functional perturbation theory. It is calculated using non-Hermitian or pseudo-Hermitian variants of the Lanczos recursion scheme, whose implementation does not require the calculation of any virtual states. Pseudopotentials (both norm-conserving and ultrasoft) are used in conjunction with plane-wave basis sets and periodic boundary conditions. Relativistic effects (spin–orbit coupling) can be included in calculations.Restrictions: Linear-response regime. Adiabatic exchange–correlation kernels only. No hybrid functionals. Collinear spin-polarized formalism is not supported, only non-collinear spin-polarized case can be used. Spin–orbit coupling cannot be used with ultrasoft pseudopotentials. No magnetism. No Hubbard U formalism. No PAW pseudopotentials.Unusual features: No virtual orbitals are used, nor even calculated. A single Lanczos recursion gives access to the whole spectrum at fixed transferred momentum.Additional comments: The distribution file of this program can be downloaded from the Quantum ESPRESSO website: http://www.quantum-espresso.org/, and the development version of this program can be downloaded via SVN from the QE-forge website: http://qe-forge.org/gf/project/q-e/.!!!!! The distribution file for this program is over 37 Mbytes and therefore is not delivered directly when download or Email is requested. Instead a html file giving details of how the program can be obtained is sent. !!!!!Running time: From a few minutes for elemental bulk systems with a few atoms in the primitive unit cell on serial machines up to many hours on multiple processors for complex systems (e.g., surfaces with high Miller indices) with dozens or hundreds of atoms.

Erratum: Electron energy loss and inelastic x-ray scattering cross sections from time-dependent density-functional perturbation theory [Phys. Rev. B88, 064301 (2013)

Erratum: Electron energy loss and inelastic x-ray scattering cross sections from time-dependent density-functional perturbation theory [Phys. Rev. B<b>88</b>, 064301 (2013)

Self-consistent continuum solvation for optical absorption of complex molecular systems in solution.

We introduce a new method to compute the optical absorption spectra of complex molecular systems in solution, based on the Liouville approach to time-dependent density-functional perturbation theory and the revised self-consistent continuum solvation model. The former allows one to obtain the absorption spectrum over a whole wide frequency range, using a recently proposed Lanczos-based technique, or selected excitation energies, using the Casida equation, without having to ever compute any unoccupied molecular orbitals. The latter is conceptually similar to the polarizable continuum model and offers the further advantages of allowing an easy computation of atomic forces via the Hellmann-Feynman theorem and a ready implementation in periodic-boundary conditions. The new method has been implemented using pseudopotentials and plane-wave basis sets, benchmarked against polarizable continuum model calculations on 4-aminophthalimide, alizarin, and cyanin and made available through the Quantum ESPRESSO distribution of open-source codes.