Mass weighted force constants

Again, for convenience, introduce a set of mass weighted force constants... 

Normal mode analysis is performed by diagonalizing the mass weighted force constant matrix, where V is a matrix representing... 

In the harmonic approximation for a molecular crystal, all atoms are oscillating about their equilibrium positions under the restraining action of a vibrational potential, V, which can be conveniently taken as just the intermolecular non-bonded potential of Eq. (1.1.25), and which obeys the translational invariance condition of Eq. (1.1.19). Let x, be the displacement of atom i from its equilibrium position in the crystal, and consider all the atoms in the reference cell and all the atoms in the surrounding cells denoted by a real space vector R. The mass-weighted force constants can be written as ... 

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