Photodissociation and formation of an ion‐pair in CH₂FCl (HCFC‐31)

Abstract

Although CH2FCl (HCFC‐31) recently became of great atmospheric importance, studies concerning its excited states are almost nonexistent. Several excited singlet states were studied (valence nσ* and Rydberg n3s, n3p, σ3s, and σ3p) through highly correlated multireference configuration interaction with singles and doubles, including extensivity correction. Comparison with the states of CH3Cl indicates a strong influence of the F atom. Potential energy curves suggest formation of an electrostatically bound complex that relaxes to a hydrogen‐bonded contact ion‐pair (HBCIP) which can decay yielding CH2F + Cl or to the ground state minimum of CH2FCl. The HBCIP has a dipole moment of 9.57 D, a CI wavefunction described as 0.65ionic + 0.20biradical and it is strongly bonded by 4.72 eV. Its H bond has characteristics of moderate and strong H bonds. The simulated absorption spectrum confirms the nσ* assignment for the first and suggests the n3s + n3pσ assignment for the second band.

Nonadiabatic molecular dynamics with subsystem density functional theory: application to crystalline pentacene

“…To date, multiple NA-MD methods have been developed, ranging from the mixed quantum-classical (MQC) methods such as Ehrenfest [63,64] and trajectory surface hopping (TSH) [65][66][67][68] techniques to semiclassical wave packet propagation and fully quantal [69] methods. Due to their simplicity, low computational cost, and reasonable accuracy, the approximate MQC techniques have found their wide use in modeling NA dynamics in many condensed-matter [70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85] and molecular systems [86][87][88][89]. However, such modeling in extended systems is often hindered by two factors: the intrinsic complexity of quantum dynamics itself and the steeply scaling costs of reliable electronic structure calculations.…”