Quantum Phase-field Open-source Package (Q-POP)
One of the core objectives for this project is the development of a software package to enable computationally efficient phase-field modeling of quantum materials. The software, which we have termed the Quantum Phase-field Open-source Package (or Q-POP for short), will enable researchers to study quantum materials and phase transitions, such as super-conductivity, metal-insulator transitions, and strongly-correlated materials, using the phase-field method using robust, state-of-the-art multi-grid methods to solve the underlying evolution and equilibrium equations. We are utilizing the FEniCS project to help in the discretization and solving of our partial differential equations. At current, we have developed a suite of solvers for a variety of equilibrium equations, such as mechanical equilibrium, which will be implemented in the final package. In addition, we are nearly complete with the development of an initial alpha release of the software with examples for the phase-field modeling of metal-insulator transitions. In addition, the flexible, easily-extendible, and maintainable phase-field modules we are generating will provide a boon to the open-source phase-field community, and lead the charge into the next generation of high-performance computing resources.
Stay tuned for a link to the initial alpha release of Q-POP.
Density Functional Theory ToolKit (DFFTK)
We worked in collaboration with two other groups at Penn State and developed a distribution of high-throughput first-principles calculation software in Python termed DFTTK. The package integrates our experiences on first-principles theoretical method and the wealth of computational software developed over the past decades. It works well with submitting DFT tasks on all popular operating systems as well as adequately performing the DFT calculations on Linux systems. We have implemented cloud calculation functions from PyMatGen and Atomate which have been developed previously. It is expected that these calculations will prove useful for researchers seeking to understand the structure and properties of materials at finite temperatures to aid in the materials by design paradigm. This program can be accessed via the following link.
BoltzTraP2Y: Atomic to Mesoscale Bridging
We developed a preliminary package to bridge the scale gap between DFT results and larger-scale simulation methods like phase-field modeling, named BoltzTraP2Y, based on previous work and the open-source software BoltzTraP2. The package takes input from DFT calculations and existing DFT databases, and calculates equilibrium chemical potential and heat capacity of electrons, as well as provides the kinetic properties including charge carrier mobility and electrical and thermal conductivities by solving the Boltzmann transport equation. We have already implemented this package to help understand various phase transitions in which the material undergoes an electronic structure change, like metal-insulator transitions. As an example, we calculated the thermodynamic and kinetic properties of Ca3Ru2O7 as an input, which yield reasonable results agreeing well with previous experimental reports. This data were further used for phase-field simulations of light-excited electron dynamics. Ultimately, the package should prove essential in expanding the power of computational materials research by bridging the critical spatial scale gap among various methods and providing valuable assistance in parametrization of phase-field models. This software can be accessed via this link.
We have received well-regarded reviews of the software. Some of which are shown below.
“Recently we used your modified code to calculated the FeNbSb half-Heusler thermoelectric properties. We found that the electrical conductivities agree with the experimental ones very well, when using the relaxation time, based on your code. Both the tau(s) and tau_1(s) work well” Dr. Rundong (Kunming University of Science and Technology, China)
Q-POP-Thermo
A new computational tool, which we have named Q-POP-Thermo, was developed for providing a fast assessment on the possible equilibrium states of structural/electronic domains and their respective volume fractions for bulk, thin films, and complex heterostructures under given thermal, electric, and mechanical conditions. This tool is more efficient than full-scale state-of-the-art phase-field simulations which can help to pinpoint phase-field simulations. Therefore, this software can provide researchers a quick initial assessment of the possible thermodynamic states of a material before carrying out full-filed expensive phase-field simulations of mesoscale domain pattern evolution.
Interested researchers can assess the documentation and source code via this link. The software is licensed under the MIT license.
Additional modification and enhancements to the code are in the pipeline which include multi-domain structures, Metal-Insulator transitions, and chemical thermodynamics.
Q-POP-Diffraction: A Software Module to Compute Diffraction Patterns of Phase-field Simulated Microstructures
The diffraction pattern of a material contains vital information about the crystal structures of underlying phases, grains, and ferroic domains. While diffraction patterns have been used for many years in an experimental setting, mesoscale microstructural models, such as phase-field, naturally reproduce real-space images of spatial distribution of these phases, structural, and ferroic domains. We have developed an approach to directly compute crystal diffraction patterns of microstructures predicted by phase-field simulations. This now enables researchers to study to predict the diffraction pattern of structural domains (like twin structures), ferroelectric vortices, and polycrystalline grain distributions to allow for direct comparison with experimental results, greatly enhancing the synergy and capabilities of mesoscale modeling. A public link to this software will be available upon acceptance of the manuscript.
PyVecAnalysis: A Software Module for Automated Identification of Topological Structures
To accelerate and standardize the analysis of topological structures, such as the polar vortices and skyrmions in PbTiO3/SrTiO3 superlattices, we developed a tool that utilizes the vector decomposition techniques, such as the Helmholtz-Hodge decomposition, to computationally identify vortices and other novel domain structures in complex heterostructures, such as skyrmions and hedgehog topological states. It is believed that such decomposition and identification techniques will lead to quicker high-throughput studies of these interesting structures for engineering applications.
The interested reader can access the software along with example calculations via this link. The software is licensed with the MIT license. A module is being developed that will be directly implemented into the Q-POP code as it is developed.
#SHAARP: Analytical and Numerical Modeling of Optical Second Harmonic Generation in Anisotropic Crystals
Electric-dipole optical second harmonic generation (SHG) is a second-order nonlinear process that is widely used as a sensitive probe to detect broken inversion symmetry and local polar order. Analytical modeling of the SHG polarimetry of a nonlinear optical material is essential to extract its point group symmetry and the absolute nonlinear susceptibilities. Current literature on SHG analysis involves numerous approximations and a wide range of (in)accuracies. We have developed an open-source package called the Second Harmonic Analysis of Anisotropic Rotational Polarimetry (♯SHAARP.si) which derives analytical and numerical solutions of reflection SHG polarimetry from a single interface (.si) for bulk homogeneous crystals with arbitrary symmetry group, arbitrary crystal orientation, complex and anisotropic linear dielectric tensor with frequency dispersion, a general SHG tensor and arbitrary light polarization. ♯SHAARP.si enables accurate modeling of polarimetry measurements in reflection geometry from highly absorbing crystals or wedge-shaped transparent crystals. The package is extendable to multiple interfaces.
The interested researcher can learn more about the software at the following link.
Multigrid Finite Element Method (FEM) Solvers
We are designing and implementing finite-element (FEM) and multigrid solvers for the phase-field equations describing the mesoscale structure evolution of quantum and functional materials with a goal to be implemented in future exascale machines.
