Analysis of the Raman frequencies close to the lambda-phase transition in NH4Cl

This study gives our analysis of the Raman frequencies for the lattice modes of v(5)TO(174 cm(-1)), v(5)TO(144 cm(-1)) and v(7)TA(93 cm(-1)), and an internal mode of v(2)(1708 cm(-1)) as functions of temperature in NH4Cl close to its lambda-phase transition (T-lambda = 241.2 K, P = 0). This analysis is performed using a power-law formula with the critical exponent beta for the order parameter according to the soft mode-hard mode coupling model.


Calculation of the Raman frequencies using volume data close to the tricritical and second order phase transitions in NH4Cl
Yurtseven, Hasan Hamit (Elsevier BV, 2009-04-30)
We calculate here the Raman frequencies of the v(5) TO(174 cm(-1)) and v(2) (1708 cm(-1)) modes as a function of temperature in the region of the tricritical (P = 1.6 kbar) and the second order (P = 2.8 kbar) phase transitions in NH4Cl. This calculation of the Raman frequencies is performed through the mode Gruneisen parameter by using the experimental length-change data obtained at zero pressure where the NH4Cl crystal exhibits a weakly first order phase transition (T-lambda = 242 K). The predicted Raman f...
Calculation of the inverse relaxation time and the activation energy as a function of temperature for the Raman modes close to the phase transitions in solid nitrogen
Yurtseven, Hasan Hamit (Elsevier BV, 2021-02-01)
The inverse relaxation time is calculated as a function of temperature for the transitions of alpha - beta (P = 0) and epsilon-delta(loc)-delta (at constant pressures) in the solid N-2. For this calculation, the observed data from the literature are used for the Raman frequency shifts and linewidths (FWHM) of the librational E-g mode (alpha - beta) and the internal modes of v(1) and v(2) (epsilon-delta(loc)-delta) in the nitrogen. From the temperature dependence of the inverse relaxation time, the activatio...
Calculation of the specific heat using the Raman frequency shifts for the solid I-II transition in benzene
Yurtseven, Hasan Hamit (Elsevier BV, 2015-06-15)
The specific heat C-p is calculated as a function of temperature using the observed Raman frequency shifts of the six lattice modes at constant pressures of 0 and 0.1 GPa for the solid I-II transition in benzene. This calculation is performed using the volume data through the mode Grfineisen parameter of each lattice mode which we determined as functions of temperature and pressure. The specific heat C-p is also calculated as a function of pressure at room temperature using the Raman frequency shifts of tho...
Estimation of protein secondary structure from FTIR spectra using neural networks
Severcan, M; Severcan, Feride; Haris, PI (Elsevier BV, 2001-05-30)
Secondary structure of proteins have been predicted using neural networks (NN) from their Fourier transform infrared spectra. Leave-one-out approach has been used to demonstrate the applicability of the method. A form of cross-validation is used to train NN to prevent the overfitting problem. Multiple neural network outputs are averaged to reduce the variance of predictions. The networks realized have been tested and rms errors of 7.7% for alpha -helix, 6.4% for beta -sheet and 4.8% for turns have been achi...
Critical behaviour of the specific heat calculated using the Raman frequencies of the lattice and internal modes near the lambda-phase transition in NH4Br
Sen, S.; Yurtseven, Hasan Hamit (Elsevier BV, 2007-05-27)
We calculate here the specific heat of NH4Br using our Raman frequency shifts for the lattice mode Of nu(7) TA (56 cm(-1)) and the internal mode Of nu(2) (1684 cm(-1)) near its lambda-phase transition (T-lambda = 234 K, P = 0). By analyzing our Raman frequency shifts, values of alpha = 0. 19 (T < T-lambda, and T > T-lambda) for the lattice mode, and alpha = 0.45 (T < T-lambda) and alpha = 0.57 (T > T-lambda) for the internal mode, are used as the values of the critical exponent for the specific heat to pred...
Citation Formats
H. H. Yurtseven, “Analysis of the Raman frequencies close to the lambda-phase transition in NH4Cl,” JOURNAL OF MOLECULAR STRUCTURE, pp. 426–429, 2007, Accessed: 00, 2020. [Online]. Available: