Theoretical Study Of Atmosphere Clusters Homogeneous Nucleation Formed By Nitric Acid And Ammonia

There is a great change in global climate these days,wide range of haze problem become more and more serious which has inseparable relation with atmospheric aerosol.Fog has great influence to the visibility which leading to frequent traffic accidents oc-curence and significant negative impact to human cardiopulmonary function.With the increase of the occurrence of fog days,the momentum of greenhouse effect starts to slow down.One of the mechanisms associated with this phenomenon is the production of large numbers of aerosols.Aerosol radiation force can change the geothermal system balance through directly scatterring and absorbbing the light and heat from the sun or changing the thickness of the cloud and the life of cloud by indirect effect.Negative radiation force of aerosol can slow down and offset the heat caused by exhaust mate-rial of greenhouse.The effect of aerosol can praise can fall.Firstly the study is related to aerosol gas-phase changing behavior of nucleation and growth.Different types of atmospheric aerosol result in different climate effect.Nitrate aerosol is an important component of atmospheric aerosol with a negative radiation force as well as sulphate aerosols.While with the mass emissions of ammonia,nitrate aerosol exist in great quan-tities which is one of the important cause of the haze.Climate effect due to aerosol has brought a series of harm to people’s normal life.Rich NH3 during haze condition can neutralize the vast majority of HNO3 and generate ammonium nitrate with seasonal feature.This article combine random algo-rithm and quantum chemistry method to preliminary simulate ultrafine aerosols nucle-ation and growth process formed by nitric acid and ammonia binary compounds.Free energy of the formation of individual clusters and free energy barrier for each additional stepwise growth were calculated to understand clusters overall stability and nucleation and growth mechanism.1.In terms of calculation method,we combine random algorithm and quantum chemistry program to search initial configurations of clusters which maturely applicated within moleculer clusters.we select the B3LYP hybrid density functional method and D3 dispersion correction effect due to weak ability to describte dispersion effect by B3LYP while DFT-D3 can be qualified to describe long-range interaction.Basic set superposition error can influence results as well,we use 6-311++G(d,p)to effectively describe the molecular orbitals and avoid to overestimate electron interaction.2.In terms of thermodynamic properties,according to the results from different stoichiometric ratio of nitric acid and ammonia proton transfer and hydrogen bond net-work are particularly important to reduce the nucleation free energy.Different free energy barrier when additional ammonia or nitric acid collide and nucleate with pre-cursor clusters suggest that nitric acid and ammonia affect slightly in growth process of atmospheric aerosol while in sulfuric acid system they play different roles obviously.The evaporation rate calculated by free formation energy can reflect stability of differ-ent molecular monomers in overall system.Generally larger cluster has higher stability,especially when m=n except that there is a transition structure from shell-structure to core-shell structure.When comparing m-n and n-m systems,the evaporation of nitric acid is lower than ammonia which indicates the bonding ability of nitric acid is stronger than ammonia.