QuantumATK is an integrated platform for atomic-scale modeling, developed since 2003 by professional software engineers in collaboration with academic researchers. It provides a wide range of simulation tools for electronic-structure calculations, including density functional theory (DFT), tight-binding models, and empirical force fields. The platform includes advanced modules for electron transport, phonon properties, spintronics, and more. It allows seamless integration of different simulation methods into complex workflows, enabling efficient and accurate modeling of materials and devices. The platform supports various simulation engines, including DFT using plane-wave (PW) or linear combination of atomic orbitals (LCAO) basis sets, semi-empirical methods, and empirical force fields. It also includes modules for ion dynamics, phonon calculations, polarization, and quantum transport. The platform is designed for both academic and industrial use, offering a user-friendly graphical interface and Python scripting for expert users. QuantumATK is particularly useful for simulating semiconductor devices, polymers, glasses, catalysis, batteries, and materials science. It supports a wide range of applications, including phonon-limited mobility calculations, electron transport in 2D devices, and multi-model simulations of lithium ion drift in battery cathodes. The platform is also used for predicting properties of new materials, such as the room-temperature photocurrent in layered Janus materials. The platform is built on a C++ backend with Python bindings, allowing for high computational performance and user-friendly scripting. It supports parallel computing for large-scale simulations and includes a variety of simulation modules for different physical phenomena. The platform is available on Windows and Linux/Unix systems and is licensed through the Synopsys Common Licensing system. QuantumATK provides a comprehensive set of tools for atomic-scale modeling, including DFT, semi-empirical methods, and empirical force fields. It supports a wide range of applications, from fundamental research to industrial applications, and is designed to be easy to use and efficient for large-scale simulations. The platform is continuously updated to include new methods and improve existing ones, making it a valuable tool for researchers and developers in the field of materials science and semiconductor technology.QuantumATK is an integrated platform for atomic-scale modeling, developed since 2003 by professional software engineers in collaboration with academic researchers. It provides a wide range of simulation tools for electronic-structure calculations, including density functional theory (DFT), tight-binding models, and empirical force fields. The platform includes advanced modules for electron transport, phonon properties, spintronics, and more. It allows seamless integration of different simulation methods into complex workflows, enabling efficient and accurate modeling of materials and devices. The platform supports various simulation engines, including DFT using plane-wave (PW) or linear combination of atomic orbitals (LCAO) basis sets, semi-empirical methods, and empirical force fields. It also includes modules for ion dynamics, phonon calculations, polarization, and quantum transport. The platform is designed for both academic and industrial use, offering a user-friendly graphical interface and Python scripting for expert users. QuantumATK is particularly useful for simulating semiconductor devices, polymers, glasses, catalysis, batteries, and materials science. It supports a wide range of applications, including phonon-limited mobility calculations, electron transport in 2D devices, and multi-model simulations of lithium ion drift in battery cathodes. The platform is also used for predicting properties of new materials, such as the room-temperature photocurrent in layered Janus materials. The platform is built on a C++ backend with Python bindings, allowing for high computational performance and user-friendly scripting. It supports parallel computing for large-scale simulations and includes a variety of simulation modules for different physical phenomena. The platform is available on Windows and Linux/Unix systems and is licensed through the Synopsys Common Licensing system. QuantumATK provides a comprehensive set of tools for atomic-scale modeling, including DFT, semi-empirical methods, and empirical force fields. It supports a wide range of applications, from fundamental research to industrial applications, and is designed to be easy to use and efficient for large-scale simulations. The platform is continuously updated to include new methods and improve existing ones, making it a valuable tool for researchers and developers in the field of materials science and semiconductor technology.