Browsing by Author "Singh, Madan"

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    Pressure Dependent Volume Change in Some Nanomaterials Using an Equation of State
    (Scientific & Academic Publishing., 2012) Singh, Madan; Tlali, Spirit; Narayan, Himanshu
    A simple equation of state (EoS) has been derived and used to study the volume expansion of some nanomaterials under the effect of pressure. Only two input parameters, namely, the bulk modulus and its first pressure derivative are required for calculations. We have considered a wide variety of nanomaterials, such as, metals [Ni (20 nm), α-Fe (nanotubes), Cu (80nm) and Ag (55nm)], semiconductors [Ge (49 nm), Si, CdSe (rock-salt phase), MgO (20nm) and ZnO], and carbon nanotube (CNT) to analyze the effects of pressure on them. The results have been compared with the available experimental data as well as with those obtained through other theoretical approaches. Excellent agreement between theoretical and experimental data, throughout the range of pressure under investigation, supports the validity of present approach.
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    A Simple, Potential-Free Model to Calculate Elastic Constants of Solids at High Temperature
    (Scientific & Academic Publishing, 2012) Singh, Madan; Narayan, Himanshu; Kumar, Munish
    A simple method for the determination of temperature dependent second order elastic constants (SOEC) of MgO, CaO, Mg2SiO4 and Grossular garnet[Ca3Al2(SiO4)3] using a potential free model based on thermodynamical relationships, has been proposed. The equations developed here are based on the linear relationship between elastic constants at temperatures higher than the Debye temperature. The extrapolated data for elastic constants at very high temperatures obtained in the present study are useful to understand the thermoelastic properties of given solids. It is found that the calculated values of elastic constants, in general, decrease with temperature. The theoretical predictions incorporating the concept of Debye temperature, reported in this paper, are well supported by the available experimental data. The proposed empirical relationship provides a method to estimate the thermoelastic properties of geophysical minerals and solids at high temperature range.