We have investigated the effect of base pairing on the electron attachment to nucleobases in bulk water, taking the guanineÀ cytosine (GC) base pair as a test case. The presence of the complementary base reinforces the stabilization effect provided by water and preferentially stabilizes the anion by hydrogen bonding. The electron attachment in bulk-solvated GC happens through a doorway mechanism, where the initial electron attached state is water bound, and it subsequently gets converted to a GC bound state. The additional electron in the final GC bound state is localized on the cytosine, similar to that in the gas phase. The transfer of the electron from the initial water-bound state to the final GC bound state happens due to the mixing of electronic and nuclear degrees of freedom and takes place at a picosecond time scale.[a] Dr.

We present the theory and implementation of a core-valence separated similarity transformed EOM-CCSD (STEOM-CCSD) method for K-edge core excitation spectra. The method can select an appropriate active space using CIS natural orbitals and near 'black box' to use. The second similarity transformation Hamiltonian is diagonalized in the space of single excitation. Therefore, the final diagonalization step is free from the convergence problem arising because of the coupling of the core-excited states with the continuum of doubly excited states. Convergence trouble can appear for the preceding core-ionized states calculation in STEOM-CCSD. A core-valence separation scheme (CVS) compatible with the natural orbital based active space selection has been implemented to overcome the problem. The CVS-STEOM-CCSD has similar accuracy as that of the standard CVS-EOM-CCSD method but comes with a lower computational cost. The modification required for the CVS scheme because of the use of CIS natural orbital is highlighted. The suitability of CVS-STEOM-CCSD for chemical application is demonstrated by simulating the K-edge spectra of glycine and thymine.

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The solid-state phase transition of a multicomponent active pharmaceutical ingredient (M-APIs), composed of (1:1) agomelatine and phosphoric acid (AGL-P), is characterized using a set of complementary techniques: in situ variable temperature powder X-ray diffraction (VT-PXRD), thermal analysis, spectroscopic techniques, and hot stage microscopy (HSM). It is observed that these dimorphic forms (AGL-P RT-form and HT-form) are enantiotropic and reversible in nature. The salt–cocrystal continuum of this system is demonstrated using ab initio powder XRD structure determination (SDPD) and dispersion corrected density functional theory (DFT-D2) analysis. Furthermore, this solid-state phase transition can be inferred as a martensitic-like transformation, where simultaneous proton migration and small conformational switching trigger the concerted molecular displacements of entire layers, leading to microscopic crystal contraction.