Theoretical study of microscopic solvation of HCl in ammonia: HCl(NH3)n, n=1–4

Abstract

The global minimum-energy and other significant structures of HCl(NH3)n (n=1–4) clusters have been identified by ab initio Monte Carlo simulated annealing. Geometries of the isomers were refined in density functional theoretical and Hartree–Fock plus second-order Møller–Plesset perturbation theoretical calculations. The energy orderings were confirmed in single-point higher-level calculations. While for HCl(NH3) only one hydrogen-bonded structure was found, for the larger clusters both ionic and molecular structures exist. Stabilization by hydrogen bonding is found to be less important in the ammonia clusters than in water clusters of similar size.

Determining the DNA stability parameters for the breathing dynamics of heterogeneous DNA by stochastic optimization

“…Finding system parameters in a complex landscape is a generic task across disciplines. [40][41][42][43][44][45][46] Typically, a given problem is cast in such a manner that the seeked-for optimum corresponds to an extremum of a functional in the complex search space. For instance, to obtain the global minimum in a rugged potential energy surface, one starts from any arbitrary point on this landscape and then moves on in the search space, following certain rules, such as accepting a move if the gradient norm for the new position decreases.…”

Bi‐stability of the master gene regulatory network of the common dendritic precursor cell: Implications for cell differentiation

“…Searching for key parameters associated with a complex landscape is a universal problem throughout disciplines. [28][29][30][31][32][33][34] Since we are interested in finding out the optimum value of a function, we execute an extremum operation on it. As an example, if our search space corresponds to a rugged surface defining the potential energy of a complex system, we take recourse to the following algorithmic steps.…”

(HCl)2(CH3OH)2(X) (X= NH3 VEYA H2O) KÜMELERİNDE PROTON DİNAMİĞİNİN TEORİK OLARAK İNCELENMESİ

“…Ayrıca, çözünme olayında son basamağın su molekülleri arasında proton transferinin olduğu belirtilmiştir [23,24]. Proton transferleri özellikle kimyasal ve biyolojik reaksiyonlarda yer aldığı için, HCl' ün iyonlaşması NH3 ve CH3OH gibi farklı hidrojen bağlı sistemlerde de çalışılmıştır [7,11,[25][26][27][28][29]. Örneğin; HCl-(CH3OH)2 ve (HCl)2-CH3OH kümeleri kuantum mekaniksel olarak çalışılmış ve frekans analizleri ve toplanmazlık özellikleri incelenmiştir [7].…”

“…(NH3)m(HCl)n sistemi de farklı hesaplama teknikleri kullanılarak çalışılmıştır [16,21,27,[32][33][34][35]. (NH3)m...HCl m=1-4 kümeleri ab inito Monte Carlo simülasyonları ile incelenmiştir ve minimum enerjili yapılar, HCl' ün hem iyonik hem de moleküler formunun olduğu daha büyük kümeler için analiz edilmiştir [27]. NH3-HCl-CH3OH trimeri ise MP2 yöntemi ile kuantum mekaniksel olarak incelenmiştir [16].…”