The warm dense hydrogen is studied in the region of the fluid–fluid phase transition in the density functional theory framework. A formalized definition of the term “molecule” based on geometry is proposed for calculating the concentration of molecules H₂ and their lifetime. Correlations between density, conductivity, H₂ molecules' lifetime, interatomic distance, and their dissociation degree are studied. The transition from molecular fluid to atomic fluid is not abrupt, while there is a drastic change in the H₂ molecules' lifetime at the density, where the phase transition occurs. It can be interpreted as the ionization of H₂ to $H_2^{+}$ plus e⁻ at the phase transition, and the start of dissociation of $H_2^{+}$ to H plus H⁺ right after the phase transition.

中文翻译：

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暖致密氢中流-流相变中 H2 分子性质的变化

在密度泛函理论框架中研究了流体-流体相变区域中的暖致密氢。提出了基于几何学的术语“分子”的正式定义，用于计算分子H ₂的浓度及其寿命。研究了密度、电导率、H ₂分子寿命、原子间距离及其解离度之间的相关性。从分子流体到原子流体的转变并不突然，而在发生相转变的密度处，H _{2分子的寿命发生了剧烈变化。}它可以解释为H ₂电离到$H_2^{+}$加上e ^-在相变和解离的开始$H_2^{+}$相变后立即变为H + H ^{+ 。}