First-principles investigation of the lattice vibrations in the alkali feldspar solid solution.

ABSTRACT: The heat capacities of Al, Si ordered alkali feldspars of different Na, K compositions were calculated using the density functional theory. The effect of the Na, K distribution, if random, ordered or clustered, on the resulting heat capacity was investigated on different cells with Ab₅₀Or₅₀ composition. For all compositions and distributions studied, the excess heat capacity of mixing is positive at low temperatures with a maximum at ~60 K. This produces an increasing excess vibrational entropy that reaches a constant value above ~200 K. The amount of the excess heat capacity of Ab₅₀Or₅₀, however, depends on the Na, K distribution. Best agreement with measured excess heat capacities is achieved, if the distribution of Na and K is either ordered o

SUBMITTER: Benisek A 

PROVIDER: S-EPMC4509561 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature