Multicomponent Cholesky Decomposition: Application to Nuclear-Electronic Orbital Theory.

The Cholesky decomposition technique is commonly used to reduce the memory requirement for storing two-particle repulsion integrals in quantum chemistry calculations that use atomic orbital bases. However, when quantum methods use multicomponent bases, such as nuclear-electronic orbitals, additional challenges are introduced due to asymmetric two-particle integrals. This work proposes several multicomponent Cholesky decomposition methods for calculations using nuclear-electronic orbital density functional theory. To analyze the errors in different Cholesky decomposition components, benchmark calculations using water clusters are carried out. The largest benchmark calculation is a water cluster (H2O)27 where all 54 protons are treated quantum mechanically. This study provides energetic and complexity analyses to demonstrate the accuracy and performance of the proposed multicomponent Cholesky decomposition method.

Simultaneous Optimization of Nuclear-Electronic Orbitals.

Accurate modeling of important nuclear quantum effects, such as nuclear delocalization, zero-point energy, and tunneling, as well as non-Born-Oppenheimer effects, requires treatment of both nuclei and electrons quantum mechanically. The nuclear-electronic orbital (NEO) method provides an elegant framework to treat specified nuclei, typically protons, on the same level as the electrons. In conventional electronic structure theory, finding a converged ground state can be a computationally demanding task; converging NEO wavefunctions, due to their coupled electronic and nuclear nature, is even more demanding. Herein, we present an efficient simultaneous optimization method that uses the direct inversion in the iterative subspace method to simultaneously converge wavefunctions for both the electrons and quantum nuclei. Benchmark studies show that the simultaneous optimization method can significantly reduce the computational cost compared to the conventional stepwise method for optimizing NEO wavefunctions for multicomponent systems.

Effects of inhalation frequency on inhalation/exposure dose of hazardous nanoparticles and toxic gases during cigarette smoking.

In this study, we measured the pollutants generations during cigarette smoking under various inhalation frequency experiment scenarios by a self-developed smoking machine. Some concepts, the effective inhaled amount and exposure amount were proposed to quantitatively estimate emission rates. Important findings include: For interval 1 s, 2 s, 3 s, 4 s and 9 s (called from 1 s to 9 s herein), effective inhaled nano-scale PN (particle number) per cigarette was 8.43E+09 #, 7.24E+09 #, 5.74E+ 09 #, 3.82E+09 # and 1.15E+09 #, it decreased linearly with interval time; exposure amount of PN in side stream smoke was 1.06E+10 #, 1.2E+10 #, 1.48E+10 #, 1.84E+10 # and 8.74E+10 #, it increased with interval time. For toxic gases, all pollutants decreased with interval time in main stream smoke. In side stream smoke, NOx and CO firstly increased with interval time and then decreased (with the highest value at 3 s interval time), while HC always increased with interval time. So, this study is useful to understand the relationship between pollution and smoking habit.

Measurement of harmful nanoparticle distribution among filters, smokers' respiratory systems, and surrounding air during cigarette smoking.

This study was undertaken to investigate the filtration effect of filter on nanoparticle and the deposition behavior of nanoparticle in the human respiratory system from the aspect of nanoparticle number during cigarette smoking. For that, two kinds of experiments were designed. One is machine experiment, a well-controlled simulated respiratory system was designed to measure the raw emission and filter effect. Another is human experiment, volunteers were asked to inhale smoke into the oral cavity only and lungs, respectively, to distinguish smoke path. Results revealed that effective inhaled nanoparticle amount of a Taishan and a Hongtaishan cigarette were 5.8E + 9 (#) and 9.4E + 7 (#), respectively. The filter's integrated reduction rate was 41.65% for nanoparticle. For Taishan cigarette, 35.4% and 41.7% of raw emitted nanoparticles were deposited in the oral cavity and lungs, respectively, the rest of 22.9% was exhaled to surrounding air. The corresponding values were 25.6%, 41.5% and 32.9%, respectively, for Hongtaishan. The current findings are expected to provide basic assessments of filter effect and harm to human and to be a warning for smokers.