In the present paper, the inelastic mean free path （IMFP） of incident electrons is calculated as a function of energy for silicon （Si）, oxides of silicon （SiO2）, SiO, and A1203 in bulk form by employing atomic/m...In the present paper, the inelastic mean free path （IMFP） of incident electrons is calculated as a function of energy for silicon （Si）, oxides of silicon （SiO2）, SiO, and A1203 in bulk form by employing atomic/molecular inelastic cross sections derived by using a semi-empirical quantum mechanical method developed earlier. A general agreement of the present results is found with most of the available data. It is of great importance that we have been able to estimate the minimum IMFP, which corresponds to the peak of inelastic interactions of incident electrons in each solid investigated. New results are presented for SiO, for which no comparison is available. The present work is important in view of the lack of experimental data on the IMFP in solids.展开更多
The isotope labeled graphene was synthesized in the concentration of 13 C carbon atom in 1%, 25%, 50%, 75% and 99%. The isotope effect on the phonon behavior in graphene was investigated based on the micro-Raman analy...The isotope labeled graphene was synthesized in the concentration of 13 C carbon atom in 1%, 25%, 50%, 75% and 99%. The isotope effect on the phonon behavior in graphene was investigated based on the micro-Raman analysis of 13 C isotope labeled graphene samples. We found that the phonon scattering is affected by the isotopic carbon atom as a point defect. Based on the experiment results, the Klemens-Callaway model and uncertainty principle were used to obtain the mean free path of the G and D phonons. The results agree with the thermal conductivity measurement by non-contact optical method and with other theoretical calculations.展开更多
We investigate the gas flows near to solid surfaces in terms of the local spatial variation in the molecular mean free path(MFP).Molecular dynamics(MD)is the appropriate scientific tool for obtaining molecularly-accur...We investigate the gas flows near to solid surfaces in terms of the local spatial variation in the molecular mean free path(MFP).Molecular dynamics(MD)is the appropriate scientific tool for obtaining molecularly-accurate dynamic information in micro and nano-scale gas flows,and has been used to evaluate the molecular mean free path of gases.In the calibration procedure,the viscosity of a gas in the homogeneous case can be recovered in our MD simulations and reach good agreement with the theoretical prediction and data from NIST.In surface-bounded gas flows,if the collisions between gas molecules and walls are counted,a spatially-varying mean free path is presented,and for the first time we have observed that the distribution of the free paths deviates from the exponential one and spikes appear in their distributions at larger Kn,i.e.in the transition flow regime.Based on elementary kinetic theory,the effective viscosity of the gas derived from the mean free path has been incorporated into the framework of the continuum-fluid dynamics equations,and micro-Couette flows are performed to demonstrate this potential application.展开更多
基金Project supported by the Indian Space Research Organization through Respond Project (Grant No.ISRO/RES/2/356/10-11)
文摘In the present paper, the inelastic mean free path （IMFP） of incident electrons is calculated as a function of energy for silicon （Si）, oxides of silicon （SiO2）, SiO, and A1203 in bulk form by employing atomic/molecular inelastic cross sections derived by using a semi-empirical quantum mechanical method developed earlier. A general agreement of the present results is found with most of the available data. It is of great importance that we have been able to estimate the minimum IMFP, which corresponds to the peak of inelastic interactions of incident electrons in each solid investigated. New results are presented for SiO, for which no comparison is available. The present work is important in view of the lack of experimental data on the IMFP in solids.
基金the National Key R&D Program (No. 2022YFC2904900)the National Natural Science Foundation of China (No. U1902221)+2 种基金the Construction of High-level Talents of Kunming University of Science and Technology,China (No. 20210172)the Leading Talents of Industrial Technology in Ten Thousand Talents Plan of Yunnan Province,Chinathe Scientist Studio of Yunnan Province,China。
基金supported by the National Natural Science Foundation of China(Grant Nos.91123009 and 10975115)the Natural Science Foundation of Fujian Province of China(Grant No.2012J06002)
文摘The isotope labeled graphene was synthesized in the concentration of 13 C carbon atom in 1%, 25%, 50%, 75% and 99%. The isotope effect on the phonon behavior in graphene was investigated based on the micro-Raman analysis of 13 C isotope labeled graphene samples. We found that the phonon scattering is affected by the isotopic carbon atom as a point defect. Based on the experiment results, the Klemens-Callaway model and uncertainty principle were used to obtain the mean free path of the G and D phonons. The results agree with the thermal conductivity measurement by non-contact optical method and with other theoretical calculations.
基金the UK’s Engineering and Physical Sciences Research Council(EPSRC)via grant no.EP/N016602/1.
文摘We investigate the gas flows near to solid surfaces in terms of the local spatial variation in the molecular mean free path(MFP).Molecular dynamics(MD)is the appropriate scientific tool for obtaining molecularly-accurate dynamic information in micro and nano-scale gas flows,and has been used to evaluate the molecular mean free path of gases.In the calibration procedure,the viscosity of a gas in the homogeneous case can be recovered in our MD simulations and reach good agreement with the theoretical prediction and data from NIST.In surface-bounded gas flows,if the collisions between gas molecules and walls are counted,a spatially-varying mean free path is presented,and for the first time we have observed that the distribution of the free paths deviates from the exponential one and spikes appear in their distributions at larger Kn,i.e.in the transition flow regime.Based on elementary kinetic theory,the effective viscosity of the gas derived from the mean free path has been incorporated into the framework of the continuum-fluid dynamics equations,and micro-Couette flows are performed to demonstrate this potential application.
