# Evidence: structural relaxation time

Parent: — · class: kinetics · names merged here: molecular relaxation time; structural relaxation time

3 papers measured or used it, 2 only mentioned it (of 207 kept papers). Papers in year order; each section heading ends with the paper's category / subcategory. Generated by tools/build_evidence.py from registry/concepts.csv and the cards; do not edit.

## 2010 Rumondor — Effects of Moisture on the Growth Rate of Felodipine Crystals in the Presence and Absence of Polymers · Solid state stability / Physical stability

[2010-rumondor-moisture-felodipine-crystal-growth-pvp-hpmcas](../../../cards/2010-rumondor-moisture-felodipine-crystal-growth-pvp-hpmcas/paper.html) · Solid state stability / Physical stability · used · as: structural relaxation time

| id | kind | content | locator |
|---|---|---|---|
| E1 | equation | Adam-Gibbs-Vogel equation: τ = τ0 exp[D T0 / (T − T(T0/Tf))] | Eq. 1, p.750 |
| R7 | record, derived (E1, E2) | log(τTg/τ)^ξ and log(crystal growth rate) + 1 versus T/Tg — drug alone (R1 data, shifted by +1 on the log scale); τ from E1 with M1 constants; Tg at each RH from M1 — sub-table below; text: good correlation obtained with a coupling constant of 0.5 | Fig. 7, p.751; text p.750-751 |

## 2013 Kestur — Evaluation of the crystal growth rate of felodipine polymorphs in the presence and absence of additives as a function of temperature · Solid state stability / Physical stability

[2013-kestur-felodipine-polymorph-crystal-growth-pvp-additives](../../../cards/2013-kestur-felodipine-polymorph-crystal-growth-pvp-additives/paper.html) · Solid state stability / Physical stability · used · as: structural relaxation time

| id | kind | content | locator |
|---|---|---|---|
| E1 | equation | molecular layers added per structural relaxation time: number of molecular layers added in one structural relaxation time, obtained from the growth rate, the structural relaxation time and the molecular size (stated in words; no formula printed) | p.12 |
| R18 | record, derived (E1) | molecular layers added in one structural relaxation time — felodipine bulk growth at 45 °C; structural relaxation time taken as 100 s; molecular radius assumed 9 Å — form I: growth rate 2.6×10⁻⁹ m/s, approximately 500 layers; form II: less than one layer at 45 °C (form II rate at 45 °C not printed; Fig. 2 has form II points at 40 and 50 °C only) | p.12 |
| C23 | claim, mechanism, authors: "supporting the supposition" | About 500 layers added per structural relaxation time at 45 °C supports the supposition that form I also exhibits the diffusionless growth mode, whereas form II, with less than one layer, does not show this fast mode [rests on: R18, R16] | p.12 |

## 2014 Trasi — Factors Influencing Crystal Growth Rates from Undercooled Liquids of Pharmaceutical Compounds · Solid state stability / Crystallization tendency

[2014-trasi-crystal-growth-rates-undercooled-pharmaceutical-liquids](../../../cards/2014-trasi-crystal-growth-rates-undercooled-pharmaceutical-liquids/paper.html) · Solid state stability / Crystallization tendency · used · as: structural relaxation time

| id | kind | content | locator |
|---|---|---|---|
| E4 | equation | structural relaxation time from viscosity and normalized growth rate: τ_α = Cη/G; normalized rate U_kin τ_α/a | p.9980 |
| R11 | record, derived (E2, E4, E7) | log(Ukin τα/a) versus ΔSm/R — the nine compounds of R10 — linear fit y = −0.6x − 0.95, R² = 0.61 (E7); text: "correlation coefficient of 0.61"; points in sub-table below | Fig. 9, p.9981; text p.9980 |

## Mentioned only

- 2010 Kestur — [2010-kestur-polymer-chemistry-felodipine-crystal-growth-inhibition](../../../cards/2010-kestur-polymer-chemistry-felodipine-crystal-growth-inhibition/paper.html) · Solid state stability / Miscibility and drug-polymer interactions (ref C29)
- 2010 Marsac — [2010-marsac-temperature-moisture-miscibility-felodipine-pvp-asd](../../../cards/2010-marsac-temperature-moisture-miscibility-felodipine-pvp-asd/paper.html) · Solid state stability / Physical stability (ref 20)