TY - JOUR
T1 - Incommensurately modulated twin structure of nyerereite Na1.64K0.36Ca(CO3)2
AU - Bolotina, Nadezhda B.
AU - Gavryushkin, Pavel N.
AU - Korsakov, Andrey V.
AU - Rashchenko, Sergey V.
AU - Seryotkin, Yurii V.
AU - Golovin, Alexander V.
AU - Moine, Bertrand N.
AU - Zaitsev, Anatoly N.
AU - Litasov, Konstantin D.
PY - 2017/4/1
Y1 - 2017/4/1
N2 - The incommensurately modulated twin structure of nyerereite Na1.64K0.36Ca(CO3)2 has been first determined in the (3+1)-dimensional symmetry group Cmcm(α00)00s with modulation vector q = 0.383a∗. Unit-cell values are a = 5.062(1), b = 8.790(1), c = 12.744(1) Å. Three orthorhombic components are related by threefold rotation about [001]. Discontinuous crenel functions are used to describe the occupation modulation of Ca and some CO3 groups. The strong displacive modulation of the O atoms in vertexes of such CO3 groups is described using x-harmonics in crenel intervals. The Na, K atoms occupy mixed sites whose occupation modulation is described in two ways using either complementary harmonic functions or crenels. The nyerereite structure has been compared both with the commensurately modulated structure of K-free Na2Ca(CO3)2 and with the widely known incommensurately modulated structure of γ-Na2CO3. The incommensurately modulated twin structure of nyerereite Na1.64K0.36Ca(CO3)2 has been first determined and then compared with the modulated structure of γ-Na2CO3.
AB - The incommensurately modulated twin structure of nyerereite Na1.64K0.36Ca(CO3)2 has been first determined in the (3+1)-dimensional symmetry group Cmcm(α00)00s with modulation vector q = 0.383a∗. Unit-cell values are a = 5.062(1), b = 8.790(1), c = 12.744(1) Å. Three orthorhombic components are related by threefold rotation about [001]. Discontinuous crenel functions are used to describe the occupation modulation of Ca and some CO3 groups. The strong displacive modulation of the O atoms in vertexes of such CO3 groups is described using x-harmonics in crenel intervals. The Na, K atoms occupy mixed sites whose occupation modulation is described in two ways using either complementary harmonic functions or crenels. The nyerereite structure has been compared both with the commensurately modulated structure of K-free Na2Ca(CO3)2 and with the widely known incommensurately modulated structure of γ-Na2CO3. The incommensurately modulated twin structure of nyerereite Na1.64K0.36Ca(CO3)2 has been first determined and then compared with the modulated structure of γ-Na2CO3.
KW - minerals
KW - carbonates
KW - nyerereite
KW - X-ray analysis
KW - incommensurately modulated structures
KW - twinning
UR - http://www.scopus.com/inward/record.url?scp=85017102346&partnerID=8YFLogxK
U2 - 10.1107/S2052520616020680
DO - 10.1107/S2052520616020680
M3 - Article
C2 - 28362292
AN - SCOPUS:85017102346
SN - 2052-5192
VL - B73
SP - 276
EP - 284
JO - Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
JF - Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
IS - 2
ER -