Computer Model of the T–х1–х2 Phase Diagram of the Paracetamol–Caffeine–Aspirin System

The influence of the type of polymorphic transformation of caffeine (catatectic or peritectic) on the topology of phase diagram prototypes for the ternary paracetamol– caffeine–aspirin (PAR–ASP–CAF) system was investigated. Given the complexity of the experimental study of such diagrams due to the narrow temperature range of existence of the low-temperature polymorphic modification of caffeine in a system with paracetamol (approximately 1°C), phase diagram prototypes were constructed by computer modeling (using the “PD Constructor” software) for three scenarios: catatectic reactions in both binary systems (PAR–CAF and CAF–ASP), peritectic reactions, and their combinations (catatectic in PAR–CAF + peritectic in CAF–ASP). Special attention was paid to the two-phase surface identified in the mixed scenario, corresponding to a change in the reaction type within the three-phase region. It is shown that the development of digital twins through computer prototyping is an effective tool for interpreting experimental thermal analysis data and for creating a “roadmap” for the study of complex pharmaceutical systems exhibiting polymorphism.