The projected hybrid orbital (PHO) method for treatment of multiple boundary atoms introduces a novel solution for handling the covalent connection between quantum mechanical (QM) and molecular mechanical (MM) regions in QM/MM calculations. By projecting the QM basis, typically adequately large for computational accuracy, onto a secondary minimal basis set on the boundary atom, it preserves electronic interactions between the two regions without system-specific parameters. Applicable in both ab initio wave function theory and density functional theory, PHO has been shown to maintain structural and electronic integrity across various systems. It offers key advantages over traditional QM/MM methods, such as avoiding modification of MM charge distribution and energy corrections, while being flexible for biochemical systems and potentially broader QM/QM embedding frameworks.

中文翻译：

---

在组合 QM/MM 计算中处理多个共价键的投影杂化轨道的方法和实现。


用于处理多个边界原子的投影混合轨道 （PHO） 方法引入了一种新的解决方案，用于处理 QM/MM 计算中量子力学 （QM） 和分子力学 （MM） 区域之间的共价连接。通过将 QM 基（通常对于计算精度来说足够大）投影到边界原子上设置的次最小基上，它可以保留两个区域之间的电子相互作用，而无需系统特定的参数。PHO 适用于从头波函数理论和密度泛函理论，已被证明可以保持各种系统的结构和电子完整性。与传统的 QM/MM 方法相比，它具有关键优势，例如避免修改 MM 电荷分布和能量校正，同时对于生化系统和可能更广泛的 QM/QM 嵌入框架具有灵活性。