Nnaemeka Ogbu | University Of Ibadan, Oyo State. Nigeria (original) (raw)
Related Authors
Iwate Prefectural University, Morioka Junior College
Uploads
Papers by Nnaemeka Ogbu
International Organization of Scientific Research, 2018
In this work, we have successfully applied one of the most effective semi-empirical interatomic p... more In this work, we have successfully applied one of the most effective semi-empirical interatomic potentials called embedded atom method EAM to calculate some thermodynamics properties of refractory metals (Nb, Ta, Mo and W). Our theoretical calculated values for mono-vacancy formation energy are in excellent agreement with the available experimental values. Among these metals, the highest f v E 1 is obtained for W. It is well known that the value of the mono-vacancy formation energy of each metal is directly proportional to its cohesive energy. i.e. the lower the cohesive energy is, the lower the mono-vacancy formation energy and vice versa. The trend exhibited by these metals whose mono-vacancy migration energies were computed revealed that migration energies are small but cannot be negative. The mono-vacancy activation energy was obtained by summing the mono-vacancy formation energy and mono-vacancy migration energy together. For all the metals considered, W has the largest values for mono-vacancy formation energy, monovacancy migration energy and mono-vacancy activation energy followed by Mo and then Ta. This could be as a result of parameter β used in the calculation. We used 8 as β for both W and Mo, while β = 6 for all other metals. The values for di-vacancy formation energy are larger than their corresponding mono-vacancy formation energy but still lower than corresponding cohesive energy of each metal. The binding energies were computed from mono-vacancy formation and divacancy formation energies. The obtained values for Nb and Ta metals are in good agreement with Zhang et al but there are no experimental values for these two metals. Experimental values are highly needed before conclusion can be drawn.
In this work, we have successfully applied one of the most effective semi-empirical interatomic p... more In this work, we have successfully applied one of the most effective semi-empirical interatomic potentials called embedded atom method EAM to calculate some thermodynamics properties of refractory metals (Nb, Ta, Mo and W). Our theoretical calculated values for mono-vacancy formation energy are in excellent agreement with the available experimental values. Among these metals, the highest f v E 1 is obtained for W. It is well known that the value of the mono-vacancy formation energy of each metal is directly proportional to its cohesive energy. i.e. the lower the cohesive energy is, the lower the mono-vacancy formation energy and vice versa. The trend exhibited by these metals whose mono-vacancy migration energies were computed revealed that migration energies are small but cannot be negative. The mono-vacancy activation energy was obtained by summing the mono-vacancy formation energy and mono-vacancy migration energy together. For all the metals considered, W has the largest values for mono-vacancy formation energy, mono-vacancy migration energy and mono-vacancy activation energy followed by Mo and then Ta. This could be as a result of parameter β used in the calculation. We used 8 as β for both W and Mo, while β = 6 for all other metals. The values for di-vacancy formation energy are larger than their corresponding mono-vacancy formation energy but still lower than corresponding cohesive energy of each metal. The binding energies were computed from mono-vacancy formation and di-vacancy formation energies. The obtained values for Nb and Ta metals are in good agreement with Zhang et al but there are no experimental values for these two metals. Experimental values are highly needed before conclusion can be drawn.
International Organization of Scientific Research, 2018
In this work, we have successfully applied one of the most effective semi-empirical interatomic p... more In this work, we have successfully applied one of the most effective semi-empirical interatomic potentials called embedded atom method EAM to calculate some thermodynamics properties of refractory metals (Nb, Ta, Mo and W). Our theoretical calculated values for mono-vacancy formation energy are in excellent agreement with the available experimental values. Among these metals, the highest f v E 1 is obtained for W. It is well known that the value of the mono-vacancy formation energy of each metal is directly proportional to its cohesive energy. i.e. the lower the cohesive energy is, the lower the mono-vacancy formation energy and vice versa. The trend exhibited by these metals whose mono-vacancy migration energies were computed revealed that migration energies are small but cannot be negative. The mono-vacancy activation energy was obtained by summing the mono-vacancy formation energy and mono-vacancy migration energy together. For all the metals considered, W has the largest values for mono-vacancy formation energy, monovacancy migration energy and mono-vacancy activation energy followed by Mo and then Ta. This could be as a result of parameter β used in the calculation. We used 8 as β for both W and Mo, while β = 6 for all other metals. The values for di-vacancy formation energy are larger than their corresponding mono-vacancy formation energy but still lower than corresponding cohesive energy of each metal. The binding energies were computed from mono-vacancy formation and divacancy formation energies. The obtained values for Nb and Ta metals are in good agreement with Zhang et al but there are no experimental values for these two metals. Experimental values are highly needed before conclusion can be drawn.
In this work, we have successfully applied one of the most effective semi-empirical interatomic p... more In this work, we have successfully applied one of the most effective semi-empirical interatomic potentials called embedded atom method EAM to calculate some thermodynamics properties of refractory metals (Nb, Ta, Mo and W). Our theoretical calculated values for mono-vacancy formation energy are in excellent agreement with the available experimental values. Among these metals, the highest f v E 1 is obtained for W. It is well known that the value of the mono-vacancy formation energy of each metal is directly proportional to its cohesive energy. i.e. the lower the cohesive energy is, the lower the mono-vacancy formation energy and vice versa. The trend exhibited by these metals whose mono-vacancy migration energies were computed revealed that migration energies are small but cannot be negative. The mono-vacancy activation energy was obtained by summing the mono-vacancy formation energy and mono-vacancy migration energy together. For all the metals considered, W has the largest values for mono-vacancy formation energy, mono-vacancy migration energy and mono-vacancy activation energy followed by Mo and then Ta. This could be as a result of parameter β used in the calculation. We used 8 as β for both W and Mo, while β = 6 for all other metals. The values for di-vacancy formation energy are larger than their corresponding mono-vacancy formation energy but still lower than corresponding cohesive energy of each metal. The binding energies were computed from mono-vacancy formation and di-vacancy formation energies. The obtained values for Nb and Ta metals are in good agreement with Zhang et al but there are no experimental values for these two metals. Experimental values are highly needed before conclusion can be drawn.