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Machine-learning-guided exploration of domain walls in the hybrid improper ferroelectric Ca3Ti2O7
Ida C. Skogvoll, Erik Fransson, Leo Ö. Westin +4
Ruddlesden-Popper phases are highly tunable and naturally layered structures, in which polarization can arise via a hybrid improper ferroelectric mechanism. This enables a complex…
Strong Impact of Halide Ordering on Structural Phase Transitions in Mixed Perovskites
Felix Uddén, Erik Fransson, Julia Wiktor +3
Mixed halide perovskites are highly versatile semiconductors with applications in photovoltaics, light-emitting diodes, and photodetectors. Understanding their thermodynamic phase…
Interplay of B-Site Off-Centering and Molecular Orientations in the Mixed Hybrid Perovskite MAGe1xSnxI3
Erik Fransson, Apinya Ngoipala, Oskar Öjstedt +3
B-site mixing is a common strategy for tuning properties of halide perovskites. In the lead-free system MAGe1-xSn_xI3, it brings tilting and off-centering into competition. Using l…
Thermal history controls the optoelectronic response of lead halide perovskites through structure and dynamics
Milos Dubajic, Xia Liang, Johan Klarbring +26
Lead halide perovskites are promising optoelectronic materials for photovoltaics, light emission and detection. Their efficiencies in PV now approach the detailed-balance limit, le…
Octahedral Tilting in Halide Double Perovskites: Disentangling Lone-Pair Chemistry and Geometric Effects
Mehmet Baskurt, Erik Fransson, Madeleine Lindvik +2
Halide double perovskites (HDPs) have emerged as promising alternatives to their lead-based counterparts. However, their structural dynamics is less explored than that of conventio…
Anion Ordering and Phase Stability Govern Optical Band Gaps in BaZr(S,Se)3
Erik Fransson, Michael Xu, Prakriti Kayastha +6
Chalcogenide perovskites have emerged as promising lead free materials for photovoltaic and thermoelectric applications. Among them, BaZrS3 has attracted particular attention due t…
Non-Markovian heat production in ultrafast phonon dynamics
Fredrik Erikssonm Yulong Qiao, Erik Fransson, R. Matthias Geilhufe +1
High-intensity THz laser pulses enable the light-mediated control of lattice vibrations by resonantly driving selected phonon modes. On ultrafast timescales, memory effects influen…
Diverse polymorphism in Ruddlesden-Popper chalcogenides
Prakriti Kayastha, Erik Fransson, Paul Erhart +1
Ruddlesden-Popper (RP) chalcogenides are stable, non-toxic candidates for optoelectronic or thermoelectric applications. The structural diversity of RP oxides is already exploited…
Predicting neutron experiments from first principles: A workflow powered by machine learning
Eric Lindgren, Adam J. Jackson, Erik Fransson +6
Machine learning has emerged as a powerful tool in materials discovery, enabling the rapid design of novel materials with tailored properties for countless applications, including…
Revealing the Low Temperature Phase of FAPbI using A Machine-Learned Potential
Sangita Dutta, Erik Fransson, Tobias Hainer +4
FAPbI is a material of interest for its potential in solar cell applications, driven by its remarkable optoelectronic properties. However, the low-temperature phase of FAPbI$_3…
A Morphotropic Phase Boundary in MAFAPbI: Linking Structure, Dynamics, and Electronic Properties
Tobias Hainer, Erik Fransson, Sangita Dutta +2
Understanding the phase behavior of mixed-cation halide perovskites is critical for optimizing their structural stability and optoelectronic performance. Here, we map the phase dia…
Dynasor 2: From Simulation to Experiment Through Correlation Functions
Esmée Berger, Erik Fransson, Fredrik Eriksson +4
Correlation functions, such as static and dynamic structure factors, offer a versatile approach to analyzing atomic-scale structure and dynamics. By having access to the full dynam…
Octahedral tilt-driven phase transitions in BaZrS chalcogenide perovskite
Prakriti Kayastha, Erik Fransson, Paul Erhart +1
Chalcogenide perovskites are lead-free materials for potential photovoltaic or thermoelectric applications. BaZrS is the most studied member of this family due to its superior…
Highly efficient path-integral molecular dynamics simulations with GPUMD using neuroevolution potentials: Case studies on thermal properties of materials
Penghua Ying, Wenjiang Zhou, Lucas Svensson +10
Path-integral molecular dynamics (PIMD) simulations are crucial for accurately capturing nuclear quantum effects in materials. However, their computational intensity and reliance o…
Untangling the Raman spectrum of cubic and tetragonal BaZrO
Petter Rosander, Erik Fransson, Nicklas Österbacka +2
Raman spectroscopy is a widely used experimental technique to study the vibrational properties of solids. Atomic scale simulations can be used to predict such spectra, but trustwor…
Impact of Surface Adsorbates and Dimensionality on Templating of Halide Perovskites
Erik Fransson, Julia Wiktor, Paul Erhart
Two-dimensional (2D) halide perovskites (HPs) are promising materials for various optoelectronic applications, yet a comprehensive understanding of their dynamics is still elusive.…
Construction and sampling of alloy cluster expansions -- A tutorial
Pernilla Ekborg-Tanner, Petter Rosander, Erik Fransson +1
Crystalline alloys and related mixed systems make up a large family of materials with high tunability which have been proposed as the solution to a large number of energy related m…
Understanding correlations in BaZrO3:Structure and dynamics on the nano-scale
Erik Fransson, Petter Rosander, Paul Erhart +1
Barium zirconate BaZrO3 is one of few perovskites that is claimed to retain an average cubic structure down to 0K at ambient pressure, while being energetically very close to a tet…
Revealing the free energy landscape of halide perovskites: Metastability and transition characters in CsPbBr and MAPbI
Erik Fransson, J. Magnus Rahm, Julia Wiktor +1
Halide perovskites have emerged as a promising class of materials for photovoltaic applications. A challenge in these applications is how to prevent the crystal structure from degr…
Quantifying Dynamic Tilting in Halide Perovskites: Chemical Trends and Local Correlations
Julia Wiktor, Erik Fransson, Dominik Kubicki +1
Halide perovskites have emerged as one of the most interesting materials for optoelectronic applications due to their favorable properties, such as defect-tolerance and long charge…
Tuning the lattice thermal conductivity in van-der-Waals structures through rotational (dis)ordering
Fredrik Eriksson, Erik Fransson, Christopher Linderälv +2
It has recently been demonstrated that MoS2 with irregular interlayer rotations can achieve an extreme anisotropy in the lattice thermal conductivity (LTC), which is for example of…
Anharmonicity of the antiferrodistortive soft mode in barium zirconate BaZrO
Petter Rosander, Erik Fransson, Cosme Milesi-Brault +6
Barium zirconate (BaZrO) is one of the very few perovskites that is claimed to retain an average cubic structure down to \SI{0}{\K}, while being energetically very close to an…
Phase transitions in inorganic halide perovskites from machine learning potentials
Erik Fransson, Julia Wiktor, Paul Erhart
The atomic scale dynamics of halide perovskites have a direct impact not only on their thermal stability but their optoelectronic properties. Progress in machine learned potentials…
Limits of the phonon quasi-particle picture at the cubic-to-tetragonal phase transition in halide perovskites
Erik Fransson, Petter Rosander, Fredrik Eriksson +3
The soft modes associated with continuous-order phase transitions are associated with strong anharmonicity. This leads to the overdamped limit where the phonon quasi-particle pictu…