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In an ab initio MD simulation, the total energy of the system is calculated at each time step using density functional theory (DFT) or another method of quantum chemistry. The forces acting on each atom are then determined from the gradient of the energy with respect to the atomic coordinates, and the equations of motion are solved to predict ...
GROMACS is a molecular dynamics package mainly designed for simulations of proteins, lipids, and nucleic acids.It was originally developed in the Biophysical Chemistry department of University of Groningen, and is now maintained by contributors in universities and research centers worldwide.
A molecular dynamics simulation requires the definition of a potential function, or a description of the terms by which the particles in the simulation will interact. In chemistry and biology this is usually referred to as a force field and in materials physics as an interatomic potential.
Quantum chemistry computer programs are used in computational chemistry to implement the methods of quantum chemistry. Most include the Hartree–Fock (HF) and some post-Hartree–Fock methods. They may also include density functional theory (DFT), molecular mechanics or semi-empirical quantum chemistry methods .
Proprietary, free academic use, source code Beckman Institute: NWChem: No No Yes Yes No No Yes No No High-performance computational chemistry software, includes quantum mechanics, molecular dynamics and combined QM-MM methods Free open source, Educational Community License version 2.0 NWChem: Protein Local Optimization Program: No Yes Yes Yes ...
In a simulation this may be implemented by using small time steps for the simulation, using a fixed number of constraint-solving steps per time step, or solving constraints until they are met by a specific deviation. When approximating the constraints locally to first order, this is the same as the Gauss–Seidel method.
The core of the software is a modular set of callable routines which allow manipulating coordinates and evaluating potential energy and derivatives via straightforward means. Tinker works on Windows, macOS, Linux and Unix. The source code is available free of charge to non-commercial users under a proprietary license.
Other simulation methods (such as replica exchange) are supported through a plug-in-based infrastructure, which also allows users to develop their own simulation algorithms and models. Desmond is also available in a graphics processing unit (GPU) accelerated version that is about 60-80 times faster than the central processing unit (CPU) version.