Quantics: A general purpose package for Quantum molecular dynamics simulations

Quantics is a general purpose program package to simulate the time-evolution of a molecular system by solving the time-dependent Schrödinger 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 Schrödinger 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 Européen de Calcul Atomique et Moléculaire (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.Quantics是一款通用程序包，可通过求解含时薛定谔方程来模拟分子体系的时间演化。其核心代码基于多种变体的多组态含时哈特里（multi-configurational time-dependent Hartree, MCTDH）算法，其中包含功能强大的多层MCTDH算法，该算法可用于传播自由度多达1000的波函数。MCTDH对哈密顿量与波函数的传统离散基组表示形式进行收缩处理，而Quantics则集成了一系列可变表象（离散变量表象，Discrete Variable Representation, DVR）网格基组与配点法。程序通过ASCII文本文件接收输入，对于带有解析势能函数的分子体系，无需额外编写代码即可运行。程序内置了用于处理复杂场景的势能函数库，用户亦可根据需求自行添加更多函数。该代码还集成了基于波函数高斯波包展开的变分多组态高斯（variational multi-configurational Gaussian, vMCG）方法，vMCG可采用“直接”模式（DD-vMCG）运行，通过多款量子化学程序实时计算势能面。除波包传播外，Quantics还可针对小型体系求解不含时薛定谔方程，也可通过求解刘维尔-冯·诺依曼方程来传播密度矩阵。本程序包附带辅助程序，用于协助搭建计算任务与分析输出结果。Quantics是英国量子动力学联合计算项目（UK Collaborative Computational Project for Quantum Dynamics, CCPQ）与欧洲E-CAM项目的社区代码，该项目是由欧洲原子与分子计算中心（Centre Européen de Calcul Atomique et Moléculaire, CECAM）运营的软件开发电子基础设施。依托这两个项目，Quantics已成为通用动力学程序的开发框架，例如支持外部表面跳跃程序调用Quantics的输入与算符接口。