turboTDDFT 2.0 Hybrid functionals and new algorithms within time-dependent density-functional perturbation theory

We present a new release of the turboTDDFT code featuring an implementation of hybrid functionals, a recently introduced pseudo-Hermitian variant of the Liouville-Lanczos approach to time-dependent density-functional perturbation theory, and a newly developed Davidson-like algorithm to compute selected interior eigenvalues/vectors of the Liouvillian super-operator. Our implementation is thoroughly validated against benchmark calculations performed on the cyanin (C21O11H21) molecule using the Gaussian 09 and turboTDDFT 1.0 codes. Program summary Program title: turboTDDFF 2.0 Catalogue identifier: AEIX_v2_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEDCv2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 2 No. of lines in distributed program, including test data, etc.: 5995995 No. of bytes in distributed program, including test data, etc.: 122184812 Distribution format: tar.gz Programming language: Fortran 95, MAI. Computer: Any computer architecture. Operating system: GNU/Linux, AIX, IRIX, Mac OS X, and other UNIX-like OS's. Classification: 16.2, 16.6, 7.7. External routines: turboTDDFT 2.0 is a tightly integrated component of the Quantum ESPRESSO distribution and requires the standard libraries linked by it: BIAS, LAPACK, FFTW, MPI. Does the new version supercede the previous version?: Yes Nature of problem: Calculation of the optical absorption spectra of molecular systems. Solution method: Electronic excited states are addressed by linearized time-dependent density-functional theory within the plane-wave pseudo-potential method. The dynamical polarizability can be computed in terms of the resolvent of the Liouvillian super-operator, using a pseudo-Hermitian variant of the Lanczos recursion scheme. As an alternative, individual eigenvalues of the Liouvillian can be computed via a newly introduced variant of the Davidson method. In both cases, hybrid functionals can now be used. Reasons for new version: To implement new features. Summary of revisions: New features implemented: 1. Hybrid functionals. 2. Pseudo-Hermitian Lanczos recursion algorithm. 3. All-new Davidson-like solver for the Liouvillian eigenvalue equation ("Casida equation"). Restrictions: Spin-restricted formalism. Linear-response regime. Adiabatic XC kernels only. Hybrid functionals are only accessible using norm-conserving pseudo-potentials. Unusual features: No virtual orbitals are used, nor even calculated. Within the Lanczos method a single recursion gives access to the whole optical spectrum; when computing individual excitations using the Davidson method, interior eigenvalues can be easily targeted. Additional comments: !!!!! The distribution file for this program is over 121 Mbytes and therefore is not delivered directly when download or E-mail is requested. Instead a html file giving details of how the program can be obtained is sent. Running time: From a few minutes for small molecules on serial machines up to many hours on multiple processors for complex nanosystems with hundreds of atoms. (C) 2014 Elsevier B.V. All rights reserved.

Rhodopsin Absorption from First Principles: Bypassing Common Pitfalls

Pablo Campomanes Ramos, Ursula Röthlisberger, Ivano Tavernelli

Bovine rhodopsin is the most extensively studied retinal protein and is considered the prototype of this important class of photosensitive biosystems involved in the process of vision. Many theoretical investigations have attempted to elucidate the role of the protein matrix in modulating the absorption of retinal chromophore in rhodopsin, but, while generally agreeing in predicting the correct location of the absorption maximum, they often reached contradicting conclusions on how the environment tunes the spectrum. To address this controversial issue, we combine here a thorough structural and dynamical characterization of rhodopsin with a careful validation of its excited-state properties via the use of a wide range of state-of-the-art quantum chemical approaches including various flavors of time-dependent density functional theory (TDDFT), different multireference perturbative schemes (CASPT2 and NEVPT2), and quantum Monte Carlo (QMC) methods. Through extensive quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations, we obtain a comprehensive structural description of the chromophoreprotein system and sample a wide range of thermally accessible configurations. We show that, in order to obtain reliable excitation properties, it is crucial to employ a sufficient number of representative configurations of the system. In fact, the common use of a single, ad hoc structure can easily lead to an incorrect model and an agreement with experimental absorption spectra due to cancelation of errors. Finally, we show that, to properly account for polarization effects on the chromophore and to quench the large blue-shift induced by the counterion on the excitation energies, it is necessary to adopt an enhanced description of the protein environment as given by a large quantum region including as many as 250 atoms.

Amer Chemical Soc2013

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

Oliviero Andreussi, Nicola Marzari, Iurii Timrov

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. (c) 2015 AIP Publishing LLC.

Amer Inst Physics2015

Rhodopsin Absorption from First Principles: Bypassing Common Pitfalls

Pablo Campomanes Ramos, Ursula Röthlisberger, Ivano Tavernelli

Amer Chemical Soc2013