By Jiushu Shao
Beijing Normal University, Beijing 100875, China

A quantum analogue of the traditional Brownian motion has been established for dissipative systems described by the system-plus-bath model. It is shown that the evolution of the system or the reduced density matrix satisfies a stochastic Liouville equation driven by complex noises. As a theoretical tool this stochastic formulation can be used to derive both approximate master equations and exact ones for specific systems. It can also be employed as a practical technique for simulating nonequilibrium dynamics numerically via a direct implementation or transforming to a deterministic algorithm a la hierarchical equations. It has been demonstrated that a mixed random-deterministic scheme allows us to calculate the zero-temperature dynamics of the spin-boson model with Ohmic dissipation. It is found that for strong dissipation the population in the localized state obeys a simple rate dynamics and time scale is proportional to the reciprocal of the cutoff frequency. This observation still awaits for further theoretical explanation.

*Supported by the National Natural Science Foundation and the Ministry of Science and Technology, China

By David Tannor
Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100 Israel

We present a method for solving both the time-independent and time-dependent Schrödinger equations based on the von Neumann (vN) lattice of phase space Gaussians. By incorporating periodic boundary conditions into the vN lattice we solve a longstanding problem of convergence of the vN method. This opens the door to tailoring quantum calculations to the underlying classical phase space structure while retaining the accuracy of the Fourier grid basis. Formally the method defeats exponential scaling with dimensionality. In the classical limit the method reaches the remarkable efficiency of 1 converged eigenstate per 1 basis functions. We illustrate the method by calculating the vibrational eigenstates for several polyatomic molecules and by simulating attosecond electron dynamics in the presence of combined strong XUV and NIR laser fields. The method also has applications to signal and image processing. This will be illustrated with several audio and image examples where large compression factors are achieved.

References

1. Shimshovitz and D. J. Tannor, Phase Space Approach to Solving the Time-independent Schrödinger Equation, Phys. Rev. Lett. 109, 070402 (2012).
2. Shimshovitz and D. J. Tannor, Phase Space Wavelets for Solving Coulomb Problems, J. Chem. Phys. 137, 101103 (2012) (Communication).
3. N. Takemoto, A. Shimshovitz and D. J. Tannor, Phase Space Approach to Laser-driven Electronic Wavepacket Propagation, J. Chem. Phys. 137, 011102 (2012) (Communication).
4. J. Tannor, N. Takemoto and A. Shimshovitz, Phase Space Approach to Solving the Schrödinger Equation: Thinking Inside the Box, Adv. Chem. Phys. 156, 1 (2014). 
5. Assémat, S. Machnes and D. J. Tannor, Double Ionization of Helium from a Phase Space (preprint).
6.  

By Daiqian Xie
Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China

While photodissociation has been extensively studied in the past, new experiments have revealed more details of the dynamics. For example, Yang and coworkers have recently employed the high resolution H-Rydberg tagging technique to measure product state-resolved differential cross sections for the photodissociation of H2O. While providing the most detailed information about dynamics, state-to-state DCSs in polyatomic photodissociation have seldom been calculated quantum mechanically, despite the existence of the photodissociation theory for more than 30 years. Recently, we developed a new set of non-adiabatically coupled potential energy surfaces for the lowest two 1A′ states of H2O at the internally contracted multi-reference configuration interaction level with the aug-cc-pVQZ basis set [1,2]. Quantum dynamical calculations carried out using the Chebyshev propagator yield absorption spectra, product state distributions, branching ratios, and differential cross sections, which are in reasonably good agreement with the latest experimental results. Besides the non-adiabatic pathway by conical intersections between the B and X states of H2O, there is another non-adiabatic pathway by the Renner-Teller coupling between the B and X states near linearity. To investigate the dissociation dynamics involving all three electronic states, a set of coupled diabatic PESs has been determined. We performed state-to-state quantum dynamics for the photodissociation of H2O in its B band involving both non-adiabatic pathways in addition to the adiabatic pathway leading to the excited OH(A) fragment[3,4]. Our dynamical results indicate that, although the Renner-Teller non-adiabatic pathway plays a relatively minor role in the dissociation, the inclusion of all three electronicstates is necessary to resolve the fine-structure population of the OH(X) fragment.

References

1. B. Jiang et al., J. Chem. Phys. (Comm.) 134, 231103 (2011)
2. B. Jiang et al., J. Chem. Phys. 136, 034302 (2012)
3. L. S. Zhou et al., J. Phys. Chem. A 117, 6940 (2013)
4. L. S. Zhou et al., J. Chem. Phys. 139, 114303 (2013)

By Donghui Zhang
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, CAS, Dalian, China 116023

Water dissociation on metal surfaces to form chemisorbed OH(ads) and H(ads) is an essential part in the steam reforming process used on a large scale by the chemical industry to convert methane (CH4) to hydrogen. It is, therefore, of great importance to have an in-depth understanding of the adsorption and dissociation process. Theoretically, with only one relatively heavy atom (O atom) involved, the scattering of this three-atom molecule on a static surface is an ideal system to carry out quantum dynamics studies beyond diatomic molecules such as H2. Recently, reduced dimensionality quantum dynamics calculations have been performed with the number of degrees of freedom included up to six, and predicted strong mode specificity, bond selectivity, and steric effects for water on Cu(111) and Ni(111). Semi-quantitative agreements were achieved between some of theoretical results and experiments. In this talk, I will present some of our recent progress made on quantum dynamics studies of chemisorption of water on static metal surfaces with full nine degrees of freedom included. Our calculations provide benchmarks for testing various approximations used to estimate chemisorption probabilities based on reduced dimensionality studies.  

By Luhua Lai
College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China

Structural based drug design has been widely used in drug discovery for leading compounds identification and optimization. Many successful applications have been reported. Various docking methods and de novo structural based drug design programs have been developed, which were all developed based on the single target binding assumption. However, drugs encounter complicated situations and a huge number of biological molecules in the human body and may cause unexpected deleterious or beneficial effects. In order to understand mechanism of drug action, disease related molecular networks need to be studied. My group has been working on the human inflammation related arachidonic acid (AA) metabolic network in order to understand its regulation mechanism and to discover better intervention strategy. We developed a multiple target optimum intervention method (MTOI) that can be used to identify key targets for drug design and to predict optimum solutions to modulate disease network with minimum side effects. Systems based network analysis prompts new directions for structure based drug design, including: (1) multiple target drug design; (2) allosteric regulating, especially activatingmolecule design; (3) rational design of binding kinetics; (4) ligand design targeting intrinsically disordered proteins, etc. The disease network models can also be used to understand traditional Chinese medicine. A few examples of how systems analysis helps to discover efficient disease intervention strategies will also be given.

By W. H. Eugen Schwarz
Physical and Theoretical Chemistry, University of Siegen, 57068 Germany
Theoretical Chemistry Center,  Tsinghua University, 100084 Beijing, China

We draw various conclusions from results of relativistically corrected computations at density-functional up to RAS-SCF-PT2-SI/SO levels on heavy atomic systems such as [UCl6]2−, AnO4, Sg@Au12, [Sg6O19]2−, Rg2, etc. Concerning in particular the periodic table of chemical elements, we stress the fact that the Usual Order of Effective Valence Orbital Energies of Atoms in Compounds for all groups 3-18 is

1s<<  2s<2p<<  3s<3p<<  3d<4s<4p<<  4d<5s<5p<< 4f<5d<6s<6p< 5f<6d<7s<7p< …..

The large energy gaps above the np shells are the result of the orbital energy order for given n: ns<np<nd<<nf, which is caused by the nuclear shielding of the core electrons, and by the valence electrons’ centrifugal force ~ ℓ2. The gaps above np  pin the periodicity of the elements through the neighboring, but chemically so different groups of the halogens, noble-gases and alkali-metals. Owing to the “d and f orbital collapses” upon increasing nuclear charge and ionic charge of the atoms, the ‘true’ orbital order differs so much from the textbook order, which holds for some of the groups 1-2 elements. 

By Jeff Skolnick
Center for the Study of Systems Biology, Georgia Institute of Technology

The intrinsic ability of protein structures to exhibit the geometric and sequence properties required for ligand binding without evolutionary selection is shown by the coincidence of the properties of pockets in native, single domain proteins with those in computationally generated, compact homopolypeptide, artificial structures, ART. The library of native pockets is covered by a remarkably small number of representative pockets (~400), with virtually every native pocket having a statistically significant match in the ART library, suggesting that the library is complete. When sequences are selected for ART structures based on fold stability, pocket sequence conservation is coincident to native. The fact that structurally and sequentially similar pockets occur across fold classes combined with the small number of representative pockets in native proteins implies that promiscuous interactions are inherent to proteins. Based on comparison of PDB and ART structures and pockets, the widespread assumption that the co-occurrence of global structure, pocket similarity, and amino acid conservation demands an evolutionary relationship between proteins is shown to significantly underestimate the random background probability. Indeed, many features of biochemical function arise from the physical properties of proteins which evolution likely fine-tunes to achieve specificity. This study suggests that a repertoire of thermodynamically (marginally) stable proteins could engage in many of the biochemical reactions needed for living systems without selection for function, a conclusion with significant implications for the origin of life.  Finally, examples of experimental validation of small molecule hits that exploit the degeneracy of ligand binding pockets are presented. Most promising is the prediction and clinical validation of the repurposing of an FDA approved drug to treat chronic fatigue syndrome.