Using the well-developed polymer self-consistent field (SCF) calculations of the “standard” model, we found that the relative stability among seven Frank–Kasper phases (A15, σ, H, Z, pσ, C14, and C15) formed by both neat diblock copolymer (DBC) A-B melts and binary DBC blends is dominated by their internal-energy densities (i.e., the repulsion between A and B blocks). This trend is also found in other SCF data (including those for the binary blends of DBC and a homopolymer) regardless of the detailed models used. We further found that variations of the Helmholtz free-energy and internal-energy curves of different FK phases are clearly correlated with the average coordination number (CN) z̅ of the Wigner–Seitz polyhedra (which is equivalent to the average number of 6-fold rotation axes) in these FK phases, and defined the internal-energy-weighted and the Helmholtz-free-energy-weighted average CNs, which can be regarded as constant depending only on the FK phase similar to z̅ but are more pertinent to its internal energy and Helmholtz free energy, respectively, than z̅. Finally, the change of the stable phase between σ and C14/C15 in binary DBC blends is mainly due to that in the interchain repulsion.

中文翻译：

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实现由纯二嵌段共聚物熔融和二元共混物形成的 Frank-Kasper 固定相的相对稳定性


使用“标准”模型的成熟聚合物自洽场 （SCF） 计算，我们发现由纯二嵌段共聚物 （DBC） AB 熔体和二元 DBC 共混物形成的七个 Frank-Kasper 相（A15、σ、H、Z、pσ、C14 和 C15）之间的相对稳定性由它们的内能密度（即 A 和 B 嵌段之间的排斥）主导。无论使用何种详细模型，其他 SCF 数据（包括 DBC 和均聚物的二元共混物的数据）也发现了这一趋势。我们进一步发现，不同 FK 相的亥姆霍兹自由能和内能曲线的变化与这些 FK 相中 Wigner-Seitz 多面体的平均配位数 （CN） z̅ （相当于 6 倍旋转轴的平均数量）明显相关，并定义了内能加权和亥姆霍兹自由能加权平均 CNs， 它可以被视为常数，仅取决于类似于 z̅ 的 FK 相，但分别比 z̅ 与其内能和亥姆霍兹自由能更相关。最后，二元 DBC 混合物中 σ 和 C14/C15 之间稳定相的变化主要是由于链间排斥的变化。