Coarse grained models for large scale atomistic simulations of spin and lattice dynamics

磁热材料体系中的耦合效应将用密度泛函理论、紧束缚和键级势方法进行研究。通过与我们的合作伙伴在此一揽子提案中的合作努力，我们希望深入了解磁热材料中的磁结构相变，并在此基础上对这类材料进行优化。在这个项目中，我们将开发具有足够精度的原子键序势，用于磁热材料的模拟。这一目标将通过从精确的密度泛函表示开始的电子结构的系统粗粒化来实现。键级势将允许O（N）分子动力学模拟，并且与DFT相比将增加额外的长度和时间尺度。这将允许模拟微观结构元素，如孪晶和晶界的动力学，以及直接评估与磁结构相变有关的能量/熵贡献。此外，在与我们的实验合作伙伴的密切合作中，我们将进行精确的全电子计算，以优化已知的磁热材料并研究可能的新磁热材料。本文研究了合金成分、应变和磁场对Y-Co-Ce-Fe系合金的影响。

Coupling effects in magnetocaloric materials systems will be investigated by density functional theory (DFT), tight binding and bond order potential methods. Through a cooperative effort with our partners in this package proposal we want to achieve an in-depth understanding of the magnetostructural phase transitions in magnetocaloric materials and based on this contribute to an optimization of this materials class. Within this project, we will develop atomistic bond order potentials with sufficient accuracy for the simulation of magnetocaloric materials. This goal will be achieved through a systematic coarse graining of the electronic structure starting from an accurate density functional representation. The bond order potential will allow for O(N) molecular dynamics simulations and will add an additional length and time scale compared to DFT. This will allow for the simulation of microstructure elements like the dynamics of twin and grain boundaries as well as for a direct evaluation of energetic/entropic contributions in connection with the magneto-structural phase transition. Furthermore, In a close collaboration with our experimental partners we will perform accurate all electron calculations in order to optimize known and investigate possible new magnetocaloric materials. The influence of alloy composition, strain and magnetic field will be studied for Y-Co Ce-Fe based systems.