Quantics: A general purpose package for Quantum molecular dynamics simulations

Abstract Quantics is a general purpose program package to simulate the time-evolution of a molecular system by solving the time-dependent Schrodinger equation. The main code is based on the multi-configurational time-dependent Hartree (MCTDH) algorithm in various variants, including the powerful multilayer-MCTDH algorithm that has been used to propagate a wavefunction for up to 1000 degrees of freedom. MCTDH uses a contraction of traditional discrete basis set representations of the Hamiltonian and wavefunction, and Quantics includes a range of variable representation (DVR) grid basis sets and collocation methods. Input is via ascii text files and for molecules with analytical potential functions no programming is required. A library of potential functions is included to treat more complicated cases, and more functions can be added as required by the user. The code also includes the variational multi-configurational Gaussian (vMCG) method that is based on a Gaussian wavepacket expansion of the wavefunction. vMCG can be run in a “direct” manner (DD-vMCG), calculating the potential energy surfaces on-the-fly using a number of quantum chemistry programs. In addition to wavepacket propagation, Quantics can solve the time-independent Schrodinger equation for small systems and can solve the Liouville–von-Neumann equation to propagate density matrices. The Package includes auxiliary programs to help set up calculations and analyse the output. Quantics is a community code of the UK Collaborative Computational Project for Quantum Dynamics (CCPQ) and the European E-CAM project, an e-infrastructure for software development run by the Centre Europeen de Calcul Atomique et Moleculaire (CECAM). Through this it has become a framework for general dynamics codes, for example enabling an external surface hopping code to use the Quantics input and operator interfaces. Program summary Program Title: Quantics Program Files doi: http://dx.doi.org/10.17632/x9dcpc2r5c.1 Licensing provisions: LGPLv3 Programming language: Fortran90. Some Fortran77, Fortran2003, C and python. Nature of problem: Solving the time-dependent Schrodinger equation for a set of nuclei allows a range of physical processes to be studied including all quantum effects. This allows an experimental signal to be given a molecular interpretation. Typical applications are scattering cross-sections or time-resolved spectra, but also rate constants and other transport properties are possible. The exact problem to be solved is defined by the Hamiltonian, which must be provided by the user, and the initial wavepacket, again defined by the user. The final analysis of the evolving wavepacket then provides the experimental signal or molecular property. Solution method: A range of methods are possible for solving the time-evolution of a wavepacket (see main text). These can be broadly described as basis-set methods, in which the wavepacket and Hamiltonian are expanded in a set of functions. Various functions are possible, including grid-based sets (DVRs and collocation), and Gaussian wavepackets. The wavepacket can then be propagated using a variety of algorithms depending on the representation chosen. These include the full numerically-exact solution, various versions of the multi-configurational time-dependent Hartree method and approximate methods such as trajectory surface hopping. Full details are given in the documentation provided with the package and in a book and a number of review articles [1,2,3]. Additional comments including restrictions and unusual features: The code has been tested on a number of linux distributions and compilers. It works best with a bash environment and a gnu gcc / gfortran compiler greater than version 4.8. The code is parallelised in parts using either OpenMP or MPI. There is a suite of test calculations to test an installation. References [1] M. H. Beck, A. Jackle, G. A. Worth, H.-D. Meyer, The multiconfiguration time-dependent Hartree method: A highly efficient algorithm for propagating wavepackets., Phys. Rep. 324 (2000) 1–105. [2] H.-D. Meyer, G. A. Worth, Quantum molecular dynamics: propagating wavepackets and density operators using the multiconfiguration time-dependent Hartree method, Theo. Chem. Acc. 109 (2003) 251–267. [3] H.-D. Meyer, F. Gatti, G. A. Worth, Multidimensional Quantum Dynamics: MCTDH Theory and Applications, Wiley-VCH, Weinheim, Germany, 2009.

[1]  H. Meyer,et al.  Calculation of H+H2 and H+D2 reaction probabilities within the multiconfiguration time-dependent Hartree approach employing an adiabatic correction scheme , 1998 .

[2]  Hans-Dieter Meyer,et al.  Multidimensional quantum dynamics : MCTDH theory and applications , 2009 .

[3]  Oriol Vendrell,et al.  Full-dimensional (15-dimensional) quantum-dynamical simulation of the protonated water dimer. I. Hamiltonian setup and analysis of the ground vibrational state. , 2007, The Journal of chemical physics.

[4]  Theoretische Chemie,et al.  On the Effect of Initial Rotation on Reactivity. A Multi-Configuration Time-Dependent Hartree (MCTDH) Wave Packet Propagation Study on the H + D2 and D + H2 Reactive Scattering Systems † , 2001 .

[5]  Gareth W Richings,et al.  A Practical Diabatisation Scheme for Use with the Direct-Dynamics Variational Multi-Configuration Gaussian Method. , 2015, The journal of physical chemistry. A.

[6]  G. Worth,et al.  Multimode quantum dynamics using Gaussian wavepackets: The Gaussian-based multiconfiguration time-dependent Hartree (G-MCTDH) method applied to the absorption spectrum of pyrazine. , 2008, The Journal of chemical physics.

[7]  U. Manthe,et al.  Wave‐packet dynamics within the multiconfiguration Hartree framework: General aspects and application to NOCl , 1992 .

[8]  Haobin Wang,et al.  The Multilayer Multiconfiguration Time-Dependent Hartree Theory , 2011 .

[9]  H. Meyer,et al.  Time‐dependent calculation of reactive flux employing complex absorbing potentials: General aspects and application within the multiconfiguration time‐dependent Hartree wave approach , 1996 .

[10]  G. Worth,et al.  Multiconfigurational system-bath dynamics using Gaussian wave packets: Energy relaxation and decoherence induced by a finite-dimensional bath , 2003 .

[11]  G. Worth,et al.  Direct quantum dynamics using variational multi-configuration Gaussian wavepackets , 2006 .

[12]  F. Parmigiani,et al.  Mechanism of ultrafast non-reactive deactivation of the retinal chromophore in non-polar solvents. , 2017, Physical chemistry chemical physics : PCCP.

[13]  Hans-Dieter Meyer,et al.  Calculation and selective population of vibrational levels with the Multiconfiguration Time-Dependent Hartree (MCTDH) algorithm , 2006 .

[14]  H. Meyer,et al.  Rotational and diffractive inelastic scattering of a diatom on a corrugated surface: A multiconfiguration time-dependent Hartree study on N2/LiF(001) , 2001 .

[15]  Hans-Dieter Meyer,et al.  A numerical study on the performance of the multiconfiguration time-dependent Hartree method for density operators , 2000 .

[16]  Michael A. Collins,et al.  Converged quantum dynamics with modified Shepard interpolation and Gaussian wave packets , 2010 .

[17]  G. Worth,et al.  Using quantum dynamics simulations to follow the competition between charge migration and charge transfer in polyatomic molecules , 2017 .

[18]  Ian R. Craig,et al.  Proton transfer reactions in model condensed-phase environments: Accurate quantum dynamics using the multilayer multiconfiguration time-dependent Hartree approach. , 2007, The Journal of chemical physics.

[19]  H. Meyer,et al.  The multiconfiguration time-dependent Hartree method generalized to the propagation of density operators , 1999 .

[20]  Haobin Wang,et al.  Multilayer formulation of the multiconfiguration time-dependent Hartree theory , 2003 .

[21]  Uwe Manthe,et al.  A multilayer multiconfigurational time-dependent Hartree approach for quantum dynamics on general potential energy surfaces. , 2008, The Journal of chemical physics.

[22]  G. Worth,et al.  A novel algorithm for non-adiabatic direct dynamics using variational Gaussian wavepackets. , 2004, Faraday discussions.

[23]  M. Ehara,et al.  Multiconfiguration time‐dependent Hartree (MCTDH) study on rotational and diffractive inelastic molecule‐surface scattering , 1996 .

[24]  Gareth W Richings,et al.  Quantum dynamics simulations using Gaussian wavepackets: the vMCG method , 2015 .

[25]  R. Kosloff.  Time-dependent quantum-mechanical methods for molecular dynamics , 1988 .

[26]  J. Light,et al.  Generalized discrete variable approximation in quantum mechanics , 1985 .

[27]  Tucker CarringtonJr..  Perspective: Computing (ro-)vibrational spectra of molecules with more than four atoms. , 2017 .

[28]  Lorenz S. Cederbaum,et al.  THE EFFECT OF A MODEL ENVIRONMENT ON THE S2 ABSORPTION SPECTRUM OF PYRAZINE : A WAVE PACKET STUDY TREATING ALL 24 VIBRATIONAL MODES , 1996 .

[29]  Lorenz S. Cederbaum,et al.  Approaches to the approximate treatment of complex molecular systems by the multiconfiguration time-dependent Hartree method , 1999 .

[30]  Hans-Dieter Meyer,et al.  Efficiently computing bound-state spectra: A hybrid approach of the multi-configuration time-dependent Hartree and filter-diagonalization methods , 2001 .

[31]  G. Worth,et al.  Molecular dynamics of pyrazine after excitation to the S2 electronic state using a realistic 24-mode model Hamiltonian , 1999 .

[32]  U. Manthe,et al.  The multi-configurational time-dependent Hartree approach , 1990 .

[33]  Lorenz S. Cederbaum,et al.  All mode dynamics at the conical intersection of an octa-atomic molecule: Multi-configuration time-dependent Hartree (MCTDH) investigation on the butatriene cation , 2001 .

[34]  M. Beck,et al.  Extracting accurate bound-state spectra from approximate wave packet propagation using the filter-diagonalization method , 1998 .

[35]  Giovanni Scalmani,et al.  Gaussian 09W, revision A. 02 , 2009 .

[36]  Raffaele Borrelli,et al.  Quantum dynamics of electron-transfer reactions: photoinduced intermolecular electron transfer in a porphyrin–quinone complex , 2012 .

[37]  D. Shalashilin,et al.  Multidimensional quantum propagation with the help of coupled coherent states , 2001 .

[38]  G. Worth,et al.  Using photoelectron spectroscopy to unravel the excited-state dynamics of benzene , 2007 .

[39]  H. Meyer,et al.  Reactive scattering using the multiconfiguration time‐dependent Hartree approximation: General aspects and application to the collinear H+H2→H2+H reaction , 1995 .

[40]  Irene Burghardt,et al.  Full quantum mechanical molecular dynamics using Gaussian wavepackets , 2003 .

[41]  Alán Aspuru-Guzik,et al.  Advances in molecular quantum chemistry contained in the Q-Chem 4 program package , 2014, Molecular Physics.