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The relationship between molecular geometries, crystal structures and charge mobilities of hexathiapentacene (HTP) and three of its derivatives (2Se-HTP, 4Se-HTP, 6Se-HTP) were studied using the density functional theory combined with a hopping mechanism at the molecular and crystal level. The effect of Se substitution on the charge mobility was discussed. The calculated results showed that the derivatives exhibit good planarity and the molecular geometries show little variation during the charge transfer process. The electron mobility is 1.20 cm2 V-1 S-1 for HTP and 2.30 cm2 V-1 S-1 for 6Se- -HTP, which are much larger than the corresponding hole ones, indicating that HTP and 6Se-HTP are good candidates for n-type organic semiconductors. However, 2Se-HTP and 4Se-HTP have comparable hole and electron motilities and are suitable for ambipolar semiconductors.

The modified attachment energy model was applied to predict the crystal morphology of hexanitrohexaazaisowurtzitane/1,3-dinitrobenzene (HNIW/DNB) cocrystal in ethanol. A double-layer interface structure was established based on experiments. Molecular dynamics simulation was employed to investigate the interaction of flat faces and ethanol solvents. We used periodic bond chains and roughness calculations to analyze the characteristics of the HNIW/DNB cocrystal. The crystal morphology of the HNIW/DNB cocrystal is mainly composed of the (001), (010), (102), and (111) faces in vacuum. The (001) face occupies the largest area (49.54%). In ethanol, the area of the (001) face increases to 68.58%. Ethanol molecules are adsorbed on the polar face through hydrogen bonding. In the slowest growth direction, two HNIW layers and one DNB layer alternately appear. The higher molecular recognition of the (001) face of HNIW/DNB resulted in this face becoming the most important growth face. Meanwhile, we also predicted the crystal morphologies of [epsilon]-HNIW and DNB in ethanol. The prediction morphologies are in excellent agreement with the experimental shapes. These simulation results can provide guidance for the recrystallization of HNIW/DNB. Key words: hexanitrohexaazaisowurtzitane, 1,3-dinitrobenzene, crystal morphology, molecular dynamics simulation, attachment energy model. Nous avons employe le modele d'energie de fixation modifie pour predire la morphologie cristalline du cocristal de HNIW/DNB dans l'ethanol. A partir de donnees experimentales, nous avons etabli que la structure de l'interface se presentait sous forme de double couche. Nous avons effectue une simulation de dynamique moleculaire pour etudier l'interaction entre les faces planes et le solvant, soit l'ethanol. Nous avons utilise la theorie des chaines de liaisons periodiques et le calcul de rugosite pour analyser les caracteristiques du cocristal de HNIW/DNB. La morphologie cristalline du cocristal de HNIW/DNB dans le vide est principalement decrite par les faces (001), (010), (102) et (111). La face (001) constitue la majorite de la surface, soit 49,54 %. Dans l'ethanol, le pourcentage de surface de la face (001) passe a 68,58 %. Les molecules d'ethanol sont adsorbees par liaison hydrogene sur la face polaire. Dans la direction de croissance la plus lente, deux couches de HNIW et une couche de DNB se succedent en alternance. Une meilleure reconnaissance moleculaire de la face (001) du cocristal de HNIW/DNB a revele que cette face devenait la face de croissance la plus importante. Parallelement, nous avons egalement predit les morphologies cristallines du [epsilon]-HNIW et du DNB dans l'ethanol. Les morphologies predites par le modele montrent une excellente concordance avec les formes observees experimentalement. Ces resultats de simulation peuvent servir a orienter les conditions de recristallisation du HNIW/DNB. [Traduit par la Redaction] Mots-cles : hexanitrohexaazaisowurtzitane, 1,3-dinitrobenzene, morphologie cristalline, simulation de dynamique moleculaire, modele d'energie de fixation., Introduction The crystal habit depends directly on the composition of crystals and become associated more closely with the physical and chemical conditions. (1-3) The study of growth habits not only [...]